Rounding to Estimate Products
💡 How to solve ▾
Round each number to the nearest ten, multiply the round numbers, and you have a fast ballpark. Track which way you rounded to judge if the real answer is a little higher or lower.
A worked example
Estimate 47 × 62: round to 50 × 60 = 3,000. You rounded up on one and down on the other, so the true answer (2,914) lands close by.
Questions people ask
When is rounding the right tool? ▾
When you want a quick sanity check or a rough figure, not an exact answer. It is ideal for catching a mistake that is off by a factor of ten.
Why is my estimate sometimes off? ▾
Rounding both numbers the same direction stacks the error. Round one up and one down when you can, and the two errors partly cancel.