CoringaWebGuides & articles
Clear, step-by-step explanations with worked examples, so you understand the math and pick the right tool.
Why Your 1 TB Drive Shows 931 GB (and Other Data Unit Mysteries)
Decimal vs binary units (GB vs GiB), why storage looks smaller than advertised, bits vs bytes for internet speed, plus a quick conversion table.
Read the guide →What Day of the Week Was I Born? Find Out in Seconds
Find the weekday of any date, past or future, and learn the math behind it: Zeller's congruence with a worked example and the mental Doomsday rule.
Read the guide →Rent or Buy a Home? A Simple Way to Decide With Real Numbers
Compare renting and buying honestly: unrecoverable costs, the 5% rule with a worked example, price-to-rent ratio and the break-even time.
Read the guide →How to Write a Check: Amount in Words, With Examples
Write the dollar amount on a check correctly: hyphens, cents as fractions, when to use "and", amounts in the thousands and how to prevent fraud.
Read the guide →How to Make a QR Code That Scans Every Time
Create a free QR code for a link, Wi-Fi or text: static vs dynamic codes, the Wi-Fi format, print size and contrast rules, and mistakes that stop scans.
Read the guide →How to Create a WhatsApp Click-to-Chat Link With a Message
Build a wa.me link that opens a chat with your number and a ready-made message. Number format, URL encoding, QR codes and tips for businesses, step by step.
Read the guide →How to Create a Strong Password That Actually Protects You
What makes a password strong in 2026: length beats complexity, random vs passphrases, entropy explained with numbers, password managers, 2FA and passkeys.
Read the guide →How to Convert Time Zones Without Mistakes (2026 Guide)
Convert time between cities with UTC offsets, avoid daylight saving traps (2026 dates for the US and Europe) and schedule meetings that work for everyone.
Read the guide →How to Calculate Percentage Increase and Decrease, Step by Step
Learn the percentage change formula, how to reverse a discount, why +10% then −10% is not zero, and the difference between percent and percentage points.
Read the guide →How to Calculate Your BMI and What the Number Really Means
The BMI formula in kg and lbs, worked examples, the official WHO categories and when BMI misleads: athletes, older adults and different populations.
Read the guide →How Much Water Should You Drink a Day? A Practical Guide
How much water you need daily by body weight, activity and climate, what the "8 glasses" rule gets wrong, official intake references and signs you need more.
Read the guide →How Many Days Between Two Dates? How to Count Them Correctly
Count days between dates without off-by-one errors: inclusive vs exclusive counting, leap years, business days, adding days to a date and spreadsheet formulas.
Read the guide →Compound Interest Formula Explained, With Real Examples
How compound interest works, the A = P(1 + r/n)^(nt) formula, monthly vs daily compounding, monthly contributions and the Rule of 72, all with worked numbers.
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