Year 3

We can round numbers to the nearest 10 or 100.
We can estimate a sum or difference before calculating.

Year 3 Unit 7

What we are learning:

• When rounding to the nearest 10, the rounded value will always be a multiple of 10. (10, 20, 30, 40 ….)
• When rounding to the nearest 10, if the units value is 0, 1, 2, 3, or 4 round DOWN to the nearest 10. If the units value is 5,6,7,8 or 9 round UP to the nearest 10.
• When rounding to the nearest 100, the rounded value will always be a multiple of 100. (100, 200, 300 …)
• When rounding to the nearest 100, if the tens value is 0,10,20,30 or 40 round DOWN to the nearest 100. If the tens value is 50, 60, 70 80 or 90 round UP to the nearest 100.
• Estimating should be very quick. Children who are given too much time to make an estimate question why they should not just calculate the actual value.
• ‘Sum’ is a different (mathematical) way of saying ‘the total found by adding’.
• ‘Difference’ is a different (mathematical) way of saying ‘the value between the two numbers’ which is found by subtracting the lower value from the higher value.
• It is important to use a range of mathematical language with your child as they will learn the meanings of different vocabulary – and then be able to use the vocabulary themselves – by hearing you use it.

ACTIVITY 1: ROUNDING NUMBERS

Activities you can do at home:

Use the Activity sheet “Rounding”. Cut out the two-digit numbers. Put the multiples of 10 (10, 20, 30 …) in a horizontal line. Place the remaining number cards in a pile and shuffle them. Take it in turns to take a number
card from the pack and work out what it will be if rounded to the nearest 10. Place the number card underneath the appropriate multiple of 10. Play the game again with the three-digit numbers but round to the nearest 100.

Using the two-digit numbers from the sheet “Rounding”. Select two numbers and place these in front of you. All ‘players’ mentally round the two numbers to their nearest tens. PUT A TIME LIMIT ON THIS (jot this down on a piece of paper) and calculate the sum of these two rounded numbers (jot this down) then mentally find the difference between these two rounded numbers (jot this down). Compare your rounded numbers and your sums and differences. Ask, Did we round to the same multiple of 10?
Calculate the actual sum/ difference between the original two-digit numbers – how close was your estimate? Play again with two different twodigit numbers or 2 three-digit numbers

Good questions to ask:

How do we know whether to round up or down to the nearest 10?
How do we know whether to round up or down to the nearest 100?

If your child:

Confuses rounding to the nearest 10 and 100, e.g. rounds 55 to 100 when you have asked them to round to the nearest 10
Draw a number line and in this case put in 0, 50 and 100 on it. Ask them to put 55 on the line and then to put their finger where the nearest 10 will be, then ask where the nearest 100 will be and explore the two answers