Rounding Numbers

Rounding to reach an approximate figure is practiced across shifting places: To the Tens Place, To the Hundreds Place, To the Thousands Place and To 2 Significant Digits. From there the work moves to estimating sums, differences, products and quotients from rounded numbers, and applies the same idea in word problems.

The most frequent error is rounding off the hundreds digit itself when told to round to the hundreds place, a mix-up over which place to act on. One zero too many or too few at the end of the answer reveals it. With 2 significant digits, numbers containing a 0 throw off where the counting starts, and the rounding lands one place early.

Before parentheses arrive as something new in Rules of Calculation, the skill of treating a number as approximate gets finished off here. The quotient-guessing built up in Division by 2-Digit Numbers is reorganized into formal rounding rules for estimating the answer to any of the four operations. That rounding skill is called on again in grade 5, when Division of Decimals asks for an answer given as an approximate figure.