# Estimate Addition Questions Using Rounding to Nearest Ten

In this worksheet, students will estimate the answer to addition sums by rounding two numbers to the nearest ten and then adding.

Key stage:  KS 2

Curriculum topic:   Number: Addition and Subtraction

Curriculum subtopic:   Estimate and Check Answers

Difficulty level:

#### Worksheet Overview

We are sometimes encouraged to estimate answers (have a sensible guess).

Estimating gives us an answer that is close to the actual answer and can help us see if an answer is likely to be correct.

We can round to the nearest 10, 100, 1,000, 10,000 etc.

In this activity, we are going to practise rounding to the nearest 10 to estimate some addition questions.

A two-digit  number that ends in five or above rounds up to the next ten.

A two-digit number that ends in four or below rounds down to the previous ten.

Example 1

Estimate the answer to the following sum by rounding the numbers to the nearest ten and then adding.

38 + 12

Answer

38 rounds up to 40

12 rounds down to 10

40 + 10 = 50

The actual answer is 50 - a great estimate!

Example 2

Estimate the answer to the following sum by rounding the numbers to the nearest ten and then adding.

64 + 55

Answer

64 rounds down to 60

55 rounds up to 60

60 + 60 = 120

The actual answer is 119 - another great estimate!

Remember, when rounding down we go back to the previous ten - 43 rounds down to 40 (not 30)

Let's have a go at some questions now - good luck!

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