Use rounding to add near multiples of 10

The ArithmeKit 27, from Buzzard Publishing's CanDoMaths collection, provides an engaging approach to teaching children how to use rounding as a strategy for adding numbers close to multiples of 10. This method is particularly useful when dealing with calculations that involve numbers just below or above these multiples, such as 15 + 9 or 23 + 17. By rounding one number up or down to the nearest ten, students can quickly perform the addition and then adjust their answer by the amount they rounded. For example, to solve 26 + 9, students would round 9 up to 10, add it to 26 to get 36, and then subtract 1 to account for the rounding, arriving at the correct answer of 35.

In addition to identifying when rounding is a useful tactic, the kit encourages students to create their own calculations where this strategy would be beneficial. It also includes exercises that involve finding missing numbers, adding 9 or 19 to a series of numbers, and observing the patterns that emerge. For instance, when you add 9 to a two-digit number, the tens place typically increases, which is a concept that can be explored through various examples and counterexamples. The kit further challenges students to solve problems with missing digits and to use all digits from 0 to 9 at least once, fostering a deeper understanding of number relationships and arithmetic operations.