Printing: use your browser's print (Ctrl+P / ⌘P). It comes out as exactly 4 A4 sheets (2 pieces of paper double-sided). No answers in here.

20 minutes, then stop

Maths B (word problems)Fri 16 October1 / 4

Putting rounding to work

Say "about how many?" out loud first, then calculate

Name Date

Three ways to round

Ordinary rounding … "about how many?"
Round up … "is it enough?" "how many buses?" (when too little is a problem)
Round down … "how many can I buy?" "how many boxes can I fill?" (leftovers do not count)
Each time, say "about how many?" out loud before you calculate.

Question 1 is already done for you

The snack limit for the trip is 800 yen. You buy things at 278, 196 and 152 yen. Is it enough?

① Round each up to the hundred: 300 + 200 + 200 = 700
② 700 is less than 800 → enough (the real total is 626 yen)

Your turn from here

2You have 1,500 yen and buy things at 468, 735 and 249 yen.
A Round each up to the hundred: what is the estimated total? Can you say "enough"?
B Estimate again, rounding each up to the ten. Is it enough?

If A goes over 1,500, the estimate may simply be too generous.

3There are 87 cookies and each box holds 12.
A Say first "about how many boxes?" (87 ≈ 90, 12 ≈ 10)
B Use long division: how many boxes are needed?

The leftover cookies need a box too.

20 minutes, then stop

Maths B (word problems)Fri 16 October2 / 4

Putting rounding to work

Name Date

4Chairs are set out 32 to a row, in 48 rows. Round both numbers to their first digit and estimate the total, then work it out exactly in long multiplication.

5The attendance at an event, rounded to the nearest hundred, was 3,600 (made up). The real number is at least what and less than what?

Around 3,600 are 3,500 and 3,700. Where are the midpoints?

6Of the whole numbers that round to 25,000 (nearest thousand), write the smallest and the largest.

The midpoint is at 500. 25,500 rounds to 26,000.

7Town A has 12,480 people and town B has 12,520, a difference of only 40. Round each to the nearest thousand. Why do the rounded numbers differ by 1,000 when the real difference is only 40?

12,500 is the border between rounding down and rounding up.

20 minutes, then stop

Maths B (word problems)Fri 16 October3 / 4

Putting rounding to work

Name Date

8You have 1,000 yen and sweets cost 48 yen each. How many can you buy, and how many yen are left? Say your estimate first (48 ≈ 50).

Money that is not enough for one more sweet buys nothing (round down).

9316 pupils ride buses. A bus holds up to 45.
A Round 45 to 50 and make an estimate.
B Use long division: how many buses are needed?
C Why do A and B differ?

One person left over still needs one more bus.

10You buy 29 cakes at 78 yen each. Round both numbers to their first digit and estimate the cost. Then work out the real cost and say whether the estimate is bigger or smaller.

20 minutes, then stop

Maths B (word problems)Fri 16 October4 / 4

Putting rounding to work

Name Date

11You buy 7 pencils at 58 yen and 3 notebooks at 147 yen. Round every price to the nearest ten and estimate the total.

Say first: "more or less than 1,000 yen?"

12The number of fourth-graders, rounded to the nearest ten, is 120. Split them into groups of 4. What is the fewest and the most groups there could be? (Leftover pupils form one more group.)

First the range: at least 115 and less than 125.

13Doing 528 x 19 in long multiplication you got 100,032. Use an estimate to check it, and if it is wrong give the right answer.

If the size is different from the estimate, doubt the digits first.