TIME CALCULATION GUIDE
Person-Hours Are Not Elapsed Time
Three people working at the same time for 30 minutes use 1.5 person-hours. Learn how that differs from elapsed time, which durations to add, and when repeats should stay.
GUIDES
Make sense of everyday calculations and comparisons
From store promotions to missing list items and time totals, these guides explain what matters and give you examples to try in our tools.
TEXT COMPARISON GUIDE
Remove Repeats, Keep the Original Order
Clean up a packing list or shortlist without sorting it. See which copy stays, when repeated lines carry useful information, and how spaces and blank lines affect the result.
TIME CALCULATION GUIDE
Why 1 Hour 30 Minutes Is 1.5 Hours
Add work, study, or video durations correctly. Learn why 1:30 is not 1.30 hours, when to carry minutes and seconds, and why rounding each entry can change the total.
TEXT COMPARISON GUIDE
What Is Missing from Your List?
Find missing and shared items without confusing a different order with a real change. Learn when spaces, repeated entries, and spelling affect the result.
TEXT COMPARISON GUIDE
Three Things to Check in a Text Diff
A small edit can change a message completely. Learn how to review changed lines, spot hidden spaces, and tell a line break from a wording change with examples you can try.
SHOPPING MATH GUIDE
20% Extra vs. 20% Off
See why 20% more product is not the same as 20% off, with a simple unit-price comparison.
SHOPPING MATH GUIDE
Buy 3, Get 1 Free: Meaning and Savings
Pay for 3, take home 4: buy 3, get 1 free is 25% off equal-priced items. See when extra items or different prices change the deal.
SHOPPING MATH GUIDE
BOGO 50% Off: The Real Discount
See why a half-price second item means 25% off when both items cost the same, and why different prices change the savings.
SHOPPING MATH GUIDE
How to Calculate Shrinkflation
Use unit prices to measure the real price increase when a package gets smaller, more expensive, or both.
SHOPPING MATH GUIDE
Percent Off vs. Dollar Off
Learn when a percentage discount or a dollar-off coupon saves more, using a simple break-even calculation.
SHOPPING MATH GUIDE
Spend $50, Get $10 Off
See how a minimum-spend coupon changes from 20% off to a smaller effective discount as your cart gets larger.
SHOPPING MATH GUIDE
Is the Bigger Package a Better Deal?
Compare price per unit to decide between package sizes, and learn when a lower unit price is not the whole answer.