← Near Enough · Lesson 4 of 4
Is it the right size?
Before you trust a total, ask what size it should be. Round everything, add the round numbers, and see whether the real answer is anywhere near.
Three things at $19.99 are about three things at $20, which is about $60. A total of $89.97 is not near $60, so something on the bill is wrong, perhaps an item rung up twice.
This takes seconds and catches the mistakes that matter: a missed decimal point, a doubled line, a number typed in the wrong box.
A till says three items at $19.99 come to $89.97. Is that the right size?
A lesson is kept once you've answered the question and written at least 8 words. Nobody grades it; it stays on this device.