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Guides and explainers on calculators, conversions and the math behind them, worked through with clear examples.
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Money· Oct 24, 2026· 18 min
Are Solar Panels Worth It in 2026 Without the Tax Credit?
With the 30% credit gone for 2026 installs, a $21,000 system pays back in about 11 years at the US average power price and under 8 in California.Math· Oct 24, 2026· 15 min
How to Calculate GPA: Semester, Cumulative and Weighted
Multiply each grade's points (A = 4.0, B+ = 3.3) by its credits, add them up and divide by total credits. Worked examples, weighted GPA and finals.Money· Oct 24, 2026· 17 min
Lease vs Buy a Car: Which Really Costs Less Over 6 Years?
On a $40,000 car, two 3-year leases cost $50,524 over 6 years; buying and keeping it cost $37,124 after resale value. How each payment works, worked out.
Earlier posts
Health & science· Oct 14, 2026· 13 min
How Is Your Due Date Calculated? LMP, Scans and IVF
How a due date is worked out: Naegele's 280-day rule, adjusting for cycle length, when a scan changes the date, IVF transfers and how few babies arrive on it.Computing· Oct 14, 2026· 10 min
Does Your Photo Show Where You Live? Check and Remove It
Phone photos can carry GPS coordinates accurate to a few metres. See what yours give away, which apps strip it, and how to remove it before you share.Computing· Oct 14, 2026· 11 min
How to Sign a PDF Without Uploading It
Sign a PDF in your browser with nothing uploaded: is an e-signature legal, how it differs from a digital signature, and when to use an e-sign service instead.Health & science· Oct 14, 2026· 14 min
What Time Should I Go to Bed? How Sleep Cycles Work
When to go to bed for your alarm: the four sleep stages, why a cycle isn't always 90 minutes, how much sleep each age needs and what the timing evidence says.Computing· Oct 11, 2026· 9 min
How to Compare Two Documents and See Every Change
Compare two versions of a contract, essay or code and see every change by line, word or letter, side by side or as track changes, without uploading anything.Health & science· Oct 11, 2026· 10 min
How Many Calories Do You Need a Day? TDEE, Explained
Your daily calories are your resting burn times an activity multiplier. Why most calculators guess low for desk workers, why a range helps, and how to check.Money· Oct 11, 2026· 11 min
How Much Have People Saved for Retirement by Age? (2025 Data)
Median and mean 401(k) and IRA balances by age from the Fed's 2025 survey, the 45% of families with no account at all, and why the median is the fair number.Money· Oct 11, 2026· 10 min
What Household Income Is Top 10%, 5% or 1%? (2025 Data)
The family income it takes to reach the top 10%, 5% and 1% in the Fed's 2025 survey, overall and by age, the median by age, and what counts as income.Productivity· Oct 10, 2026· 11 min
Do ATS Reject Resumes? The 75% and 6-Second Myths
Do applicant tracking systems really reject 75% of resumes, and do recruiters look for 6 seconds? Where both numbers came from and what the evidence says.Health & science· Oct 10, 2026· 10 min
How to Meditate for Beginners: Your First 5 Minutes
How to meditate as a beginner: what to do in your first five minutes, why a wandering mind is the practice, how often to sit, and what the evidence says.Money· Oct 10, 2026· 10 min
Net Worth by Age in 2025: What the Fed's New Survey Says
Median and average net worth by age from the Fed's 2025 survey: $33,000 under 35, $504,900 at 75+, what the top 10% takes, and why the average misleads.Money· Oct 10, 2026· 10 min
My Inflation Rate: Why Yours Isn't the Official Number
Your personal inflation rate depends on what you buy. How CPI weights work, a commuter vs a renter priced with BLS data, the 2026 gas spike and your raise.Computing· Oct 9, 2026· 12 min
How to Encrypt a File with a Password and Send It Safely
Lock a file or message with a long passphrase in your browser, then send the file one way and the password another. What protects it, and what doesn't.Health & science· Oct 9, 2026· 10 min
How Much Protein on Ozempic, Wegovy or Zepbound?
How much protein to eat while losing weight on a GLP-1: the 2025 advisory's 1.2 to 1.6 g/kg, which weight to use, a worked example and 100 g in real food.Health & science· Oct 9, 2026· 12 min
Missed a Wegovy, Ozempic, Zepbound or Mounjaro Dose? Label Rules
How late each label lets you take a missed GLP-1 dose: 4 days for Zepbound and Mounjaro, 5 for Ozempic, 2 days before the next one for Wegovy.Math· Oct 9, 2026· 13 min
Multiplication Chart Patterns: Times Tables Tricks That Work
A 12×12 multiplication chart holds 78 facts, and only 21 are hard. The patterns that give you the rest, the 7 × 8 trick, and how to practise what's left.Computing· Oct 9, 2026· 10 min
How Long Should a Password Be? What NIST Says Now
NIST now asks for at least 15 characters, with no symbol rules and no forced changes. What the standard says, the maths of length, and passphrases.Computing· Oct 9, 2026· 8 min
How to Merge PDFs Without Uploading Them
Combine PDF files on a Mac, iPhone, Windows PC or in your browser without sending them to anyone's server. Built-in ways, page order, file size and pitfalls.Computing· Oct 9, 2026· 9 min
Is It Safe to Scan a QR Code? How to Check Where It Goes
Most QR codes are fine, but stickers on parking meters and codes in emails are a known scam. How quishing works and how to read a link's real domain first.Style· Oct 9, 2026· 11 min
What Colours Go With Navy (and Why They Work)
Navy goes with almost anything because it acts like a neutral. The pairings that work best, the ones that need care, and what colour studies really show.Computing· Oct 9, 2026· 9 min
How to Compress an Image to 100 KB (or 50 KB, 20 KB)
Job portals and visa forms want photos under 100 KB, 50 KB or 20 KB. What makes a file small, a worked example with real numbers, and the mistakes to avoid.Computing· Oct 9, 2026· 12 min
Cron Syntax Explained, With Examples You'll Actually Use
Read any cron expression field by field, copy 14 everyday schedules (every 5 minutes, weekdays at 9), and avoid the traps that make jobs run at the wrong time.Computing· Oct 9, 2026· 11 min
Why Some Keys Don't Register: Ghosting and Key Rollover
Hold several keys and one goes missing, or a phantom appears. How key matrices, diodes, 6KRO and NKRO work, and how to test your own keyboard.Computing· Oct 9, 2026· 10 min
Mic Not Working? Fixes for Chrome, Windows, Mac and Phones
Test your mic in the browser first, then fix it in order of likelihood: site permission, Windows or Mac privacy, wrong input, a busy app, Bluetooth, phones.Computing· Oct 9, 2026· 13 min
Webcam Not Working? Fixes for Chrome, Windows, Mac and Phones
Test your webcam in the browser, then fix it in order: site permission, Windows or Mac privacy, wrong camera, a busy app, shutter, driver, USB, light.Health & science· Oct 9, 2026· 12 min
Wegovy vs Zepbound: How Much Weight People Lost in the Trials
The STEP 1 and SURMOUNT-1 trials in numbers: average weight loss, who reached 5 to 20%, side effects, the head-to-head trial and what happened after stopping.Computing· Oct 9, 2026· 8 min
What Is a HEIC File, and How Do You Open It?
HEIC is the photo format iPhones save by default. Why Windows, Android and upload forms often can't open it, and the cleanest ways to turn it into a JPG.Computing· Oct 8, 2026· 6 min
How to Edit Photos Without Uploading Them
Crop, adjust, blur and add text to photos in your browser without sending them anywhere: what EXIF location data is, and how to check nothing is uploaded.Math· Oct 8, 2026· 6 min
GCF vs LCM, Explained with Examples (and When You Need Each)
The greatest common factor and least common multiple, worked three ways (listing, prime factors, Euclid's algorithm), and which one a problem needs.Computing· Oct 8, 2026· 7 min
Permission Denied in Linux: How to Read ls -l and Use chmod
Why a script says Permission denied, how to read the rwx columns in ls -l, and how to fix it with chmod u+x or numeric modes such as 755 and 644.Health & science· Oct 8, 2026· 7 min
How to Print or Save a Growth Chart for Your Child's Doctor
Height, weight and BMI-for-age percentiles on the WHO and CDC charts, what a percentile does and doesn't mean, and how to print or save one report as a PDF.Health & science· Oct 7, 2026· 7 min
Cups to Grams: Why a Cup of Flour Isn’t a Cup of Sugar
Why cups to grams depends on the ingredient: USDA cup weights, how spooning or scooping flour changes them by up to 23%, and when it's worth weighing instead.Math· Oct 7, 2026· 7 min
How to Add, Subtract, Multiply and Divide Fractions
Fractions step by step: simplify with the GCF, add unlike denominators with the LCD, multiply, divide with keep-change-flip, and handle mixed numbers.Math· Oct 7, 2026· 7 min
How to Calculate Percentage Change, and Why −10 to −5 Is +50%
Percentage change step by step: increases, decreases, negative starting values, change vs difference, points vs percent, and the mistakes that trip people up.Productivity· Oct 7, 2026· 8 min
PST, PDT and IST: How Time Zones and Daylight Saving Work
UTC offsets, why the US–India gap flips between 12½ and 13½ hours, the weeks the US and Europe disagree, IANA zone names, and when working hours overlap.Productivity· Oct 7, 2026· 8 min
Chess Clock Rules: Increment, Delay, Blitz and Rapid Explained
How chess clocks work: Fischer increment vs Bronstein vs simple delay, FIDE blitz, rapid and standard categories, and which time control to pick.Computing· Oct 7, 2026· 10 min
Chrome's Built-in AI (Gemini Nano): What It Can and Can't Do
Chrome now ships a small AI model that runs on your own computer. What it's good at, where it falls short, which APIs are ready, and when to use your own key.Computing· Oct 7, 2026· 9 min
Common JSON Errors and How to Fix Each One
Trailing commas, single quotes, comments, NaN, escaped strings and big numbers that change: why JSON rejects each one, and the fix that works.Productivity· Oct 7, 2026· 10 min
Dyslexia-Friendly Fonts: What the Research Actually Says
OpenDyslexic, Lexend and Atkinson Hyperlegible checked against the studies, and why spacing and text size matter more than the font itself.Health & science· Oct 7, 2026· 8 min
How to Read an AGP Report, Step by Step
A walk through the one-page ambulatory glucose profile (AGP) from a CGM: data check, time in ranges, glucose metrics, the percentile curve and daily views.Productivity· Oct 7, 2026· 8 min
How to Split Household Chores Fairly (Mental Load Included)
What research says about who does the housework and the mental load, plus a practical way to split chores by time, take turns and talk about it calmly.Productivity· Oct 7, 2026· 10 min
How to Use a Teleprompter Without Sounding Like You're Reading
Set the right speed in words per minute, keep your eyes near the lens, and format a script for the ear, so a teleprompter read sounds like talking.Math· Oct 7, 2026· 10 min
Math Fact Fluency: Timed Practice, Spacing and Worksheets
What math fact fluency means, what research says about timed practice and math anxiety, and how to use short, mixed worksheets and answer keys well.Computing· Oct 7, 2026· 11 min
Mermaid Flowcharts and Sequence Diagrams: A Practical Guide
Write Mermaid flowcharts and sequence diagrams that render first time: shapes, arrows, subgraphs, alt and loop blocks, and the errors that break them.Productivity· Oct 7, 2026· 9 min
Pomodoro vs Flowtime: What the Research on Breaks Says
Classic Pomodoro, Flowtime and a chess-clock break budget compared: what studies on breaks and attention found, and how to pick the one that suits you.Health & science· Oct 7, 2026· 8 min
Tabata vs HIIT: What the Original Study Did and How to Time It
What the 1996 Tabata study actually tested, how gym Tabata differs, and how to time Tabata, 30/30, EMOM, boxing rounds and sprint intervals safely.Health & science· Oct 7, 2026· 9 min
Time in Range Explained: What 70–180 mg/dL Means
What blood sugar time in range measures, the international consensus targets, how it lines up with A1C and GMI, and what finger-stick readings can tell you.Productivity· Oct 7, 2026· 8 min
Visual Routine Charts for Kids: Mornings and Bedtimes That Stick
Why picture routine charts help children through mornings and bedtimes, what research on visual schedules and sleep says, and how to make one by age.Productivity· Oct 3, 2026· 6 min
How to Make a Vision Board You'll Actually Look At
A step-by-step guide to a vision board that changes what you do, not just how you feel, using what psychology research says about goals and plans.Productivity· Oct 3, 2026· 6 min
Vision Board Ideas for 2027: 60 Captions and 3 Real Examples
Sixty vision board ideas you can steal, grouped by life area, plus three real example boards and the small changes that make a board worth looking at every day.Computing· Jul 18, 2026· 2 min
DORA Metrics Explained: The Four Keys to Delivery Performance
Deployment frequency, lead time, change failure rate and time to restore: what the four DORA metrics measure, how to read them and improve them honestly.Health & science· Jul 18, 2026· 3 min· Updated Oct 2026
How to Measure Penis Size: Bone-Pressed vs Non-Bone-Pressed
A clinical guide to measuring penile length and girth the way research studies do, including the bone-pressed vs non-bone-pressed difference.Computing· Jul 18, 2026· 2 min
What LLM Tokens Really Cost (and How to Estimate Your Bill)
Tokens, context windows, input vs output pricing: how large language model costs add up, and how to estimate your monthly bill before it surprises you.Math· Jul 18, 2026· 2 min
Percentage Points vs Percent: The Difference Explained
A rate went from 4% to 5%: is that a 1% or a 25% increase? Both. The difference between percent and percentage points, and how to get it right.Math· Jul 18, 2026· 3 min
Percentiles Explained: What 'Top 10%' Really Means
Percentiles are everywhere, from growth charts to test scores, and most people read them slightly wrong. What a percentile does and doesn't tell you.Money· Jul 18, 2026· 3 min
Prepay or Refinance? How to Choose the Cheaper Path
Extra payments and refinancing both save interest, but they win in different situations. How to decide which one actually saves you more.Math· Apr 18, 2025· 4 min· Updated Oct 2026
Understanding Euler's Identity: The Most Beautiful Equation
Explore Euler's Identity, e^(iπ) + 1 = 0, and why this equation linking five fundamental constants is called the most beautiful in math.Math· Apr 11, 2025· 4 min
Order of Operations (PEMDAS/BODMAS): Why It Matters
Understand the order of operations (PEMDAS/BODMAS): the rules for parentheses, exponents, multiplication, division, addition, and subtraction.Math· Apr 4, 2025· 5 min· Updated Oct 2026
The Power of Exponentials: Growth and Decay in Nature and Finance
Explore exponential functions and their profound impact on modeling real-world phenomena, from population growth and radioactive decay to compound interest.Computing· Mar 28, 2025· 4 min· Updated Apr 2025
Introduction to Functions in Programming
Learn functions in programming: what they are, why they're used (DRY), how to define and call them, and how parameters and return values work.Money· Mar 21, 2025· 4 min· Updated Apr 2025
Good Debt vs. Bad Debt: Making Smart Borrowing Decisions
Not all debt is equal: the difference between good debt, which can grow your net worth, and bad debt, which usually doesn't, and how to manage both.Computing· Mar 14, 2025· 4 min· Updated Apr 2025
Data Types in Programming: Integers, Floats and Strings
Learn about fundamental data types in programming - integers, floating-point numbers, and strings. Understand why types matter and how they're used.Math· Mar 7, 2025· 4 min· Updated Oct 2026
Pythagorean Theorem Explained with Real-World Examples
The Pythagorean theorem (a² + b² = c²) explained: how this geometric principle applies to right-angled triangles, with practical examples.Money· Feb 28, 2025· 4 min· Updated Apr 2025
Budgeting Basics: Tracking Expenses and Creating a Plan
Take control of your money with budgeting basics: track where it goes and build a realistic spending plan that reaches your goals.Computing· Feb 21, 2025· 4 min· Updated Apr 2025
What is an Algorithm? A Beginner's Guide
Demystify the term 'algorithm'. Learn what algorithms are, why they're essential in computer science and everyday life, and see simple examples.Health & science· Feb 14, 2025· 4 min· Updated Oct 2026
Newton's Laws of Motion in Everyday Life
Discover how Sir Isaac Newton's three fundamental laws of motion explain the physics behind common occurrences, from riding a bike to hitting a baseball.Money· Feb 7, 2025· 4 min· Updated Apr 2025
Understanding Compound Interest: Make Your Money Work for You
Learn the magic of compound interest – how earning interest on your interest can significantly accelerate the growth of your savings and investments over time.Computing· Jan 31, 2025· 4 min· Updated Oct 2026
Beyond Base 10: Converting Numbers to Hexadecimal and Octal
Explore number systems beyond binary and decimal. Learn how to convert to hexadecimal (base-16) and octal (base-8), commonly used in computing.Money· Jan 24, 2025· 3 min· Updated Apr 2025
Simple Savings Strategies Anyone Can Start Today
Building savings doesn't have to be complicated. Discover easy, actionable strategies to start saving money consistently, regardless of your income.Money· Jan 17, 2025· 4 min· Updated Apr 2025
How Mortgages Work: Principal, Interest & Amortization
Demystify home loans by understanding the core concepts of principal, interest rates, and how amortization schedules dictate your payments.Computing· Jan 10, 2025· 3 min· Updated Oct 2026
Binary to Decimal and Back: Understanding Number Systems
Learn how to convert numbers between binary (base-2) and decimal (base-10) systems, the foundation of digital computing.