Rounding: closest to

Prior knowledge.

Background

This activity is an introductory exercise designed to introduce students to the idea of approximate numbers and rounding. It is knowledge based.  This exercise is about rounding numbers to the nearest 10 or 100and introduces students to talking about the approximate size of numbers. In doing this it also introduces them to a new symbol (≈ or the ‘squiggly equals’). Teachers need to be aware that this symbol needs to be used in the context of a problem, with the questions in this exercise being a very simple class of these.

Rounding numbers can only be sensibly done in a context.  672 can be correctly rounded to 670 adn also to 700, the context of the problem determines whichis more sensible. If taken out of the context of the problem, and the numbers in that problem, its use can lead to some nonsensical statements. For example, saying that 150 is approximately 200, or pi (3.1415928…) is close to zero is not very helpful mathematically. However in the context of the problem 47 ÷ 123,456,789 saying that 47 ≈ 0, so the answer is approximately zero does make sense

Comments on the Exercise