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Abacus · Ages 7+ · Set A
Take away, then add back
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Goal: 15 min
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Remember: Take away, then add back. If you land on the start, your answer is right.

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Read the story, then answer.

Checking the bead boxThe fair was nearly over, and Mia and Ben counted their bead box. That morning there had been 71 beads in it. They had sold 24, so how many were left? Ben worked it out on the frame and said 47. Mia asked if he had checked it. Her trick was to add the sold beads back on. If 47 and 24 made 71, the answer was right. Later Ben raced through another sum, 83 take away 49, and wrote 46 in a flash. He saw three ones and nine ones and took the small from the big. But three ones cannot take away nine, so he should have borrowed.
1
There were 71 beads. They sold 24. 71 - 24 =
2
Mia adds the sold beads back on. 47 + 24 =
3
If you add back what you took away and land on the start, the answer is right.
TrueFalse
4
Ben says 83 - 49 = 46. Mia adds back: 46 + 49 = 95. Is Ben right?
Yes, because 95 is bigNo, because 95 is not 83Yes, because 46 is small

On the frame

A good checker always lands home.

5
Which frame shows where 47 + 24 lands? The top row is tens.
A
B
C
6
The frame shows 62. Take away 35. 62 - 35 =
7
Now add back on the frame. 27 + 35 =
8
Check 84 - 29 = 55. Add back: 55 + 29 =
9
Which add back checks 72 - 38 = 34?
34 + 7234 + 3872 + 38

Be the checker

10
Ben's answer 46 was right for 83 - 49.
TrueFalse
11
Ben says 75 - 38 = 43. Add back: 43 + 38 =
12
Now fix it. 75 - 38 =
13
Join each sum to the sum that checks it.
  1. 170 - 25
  2. 260 + 18
  3. 392 - 47
  • A78 - 18
  • B45 + 47
  • C45 + 25
14
Check big ones too. 305 - 128 =
15
Write a take away sum. Then write the add back that checks it.
Scan the code at the top to mark this sheet on screenTake a photo of your answers or type them. It is marked for you automatically, and your score is kept.
Answer key · Set A
Take away, then add back
147 Open a ten to take away 4 ones. That leaves 4 tens and 7 ones.
271 7 + 4 = 11, so a ten carries up. Then 4 + 2 + 1 = 7 tens. She lands on 71.
3True Adding and taking away undo each other, so you land back home.
4No, because 95 is not 83 Adding back should land on 83. It landed on 95, so Ben's answer has a slip.
5C 7 ones and 4 ones make 11, so a ten carries. The frame shows 7 tens and 1 one. Frame B forgot the carry.
627 Open a ten: 5 tens and 12 ones. 12 - 5 = 7 ones and 5 - 3 = 2 tens.
762 7 + 5 = 12, so a ten carries. 2 + 3 + 1 = 6 tens. It lands on 62, so 27 was right.
884 5 + 9 = 14, so carry a ten. 5 + 2 + 1 = 8 tens. It lands on 84, so 55 was right.
934 + 38 Add back what you took away: 34 + 38 should land on 72.
10False 46 + 49 = 95, not 83. The right answer is 34.
1181 3 + 8 = 11, so carry a ten. 4 + 3 + 1 = 8 tens. It lands on 81, not 75.
1237 Open a ten: 6 tens and 15 ones. 15 - 8 = 7 and 6 - 3 = 3. Check: 37 + 38 = 75.
131-C, 2-A, 3-B To check a take away, add the part back. To check an add, take a part away.
14177 Open the hundred, then a ten: 2 hundreds, 9 tens, 15 ones. 15 - 8 = 7, 9 - 2 = 7, 2 - 1 = 1. Check: 177 + 128 = 305.
15Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.