Adding and Taking Away to 100
Primary 2 · Mathematics
Adding and Taking Away to 100
Lesson 3 of 3
14 min
Byiringiro brought 53 bananas to the market. He sold 27 of them.
He starts with the ones: 3 take away 7. But 3 is smaller than 7!
He does not give up. He knocks next door and borrows. Watch how.
When the top ones are big enough, taking away is quick.
68 - 25. Ones: 8 − 5 = 3. Tens: 6 − 2 = 4. Answer: 43.
Start on the right, with the ones, just like in adding.
Ones: 3 - 7. You cannot do it. So borrow one ten.
53 is 5 tens and 3 ones. Untie one bundle of ten. Now it is 4 tens and 13 ones.
It is still 53! Nothing was lost. The ten only changed its clothes.
Now take away:
Ones: 13 - 7 = 6. Tens: 4 - 2 = 2.
Answer: 26. Byiringiro has 26 bananas left.
26 + 27 = 53. That is the number he started with, so your answer is right.
Always check like this. It takes ten seconds and it catches every mistake.
Ones: 2 - 8. Too small. Borrow one ten, so 42 becomes 3 tens and 12 ones.
Ones: 12 − 8 = 4. Tens: 3 − 1 = 2. Answer: 24.
Check: 24 + 18 = 42. Correct.
Ones: 0 - 6. There is nothing there to take from. Borrow one ten.
70 becomes 6 tens and 10 ones.
Ones: 10 − 6 = 4. Tens: 6 − 2 = 4. Answer: 44.
Check: 44 + 26 = 70. Correct.
In 53 - 27 the ones are 3 - 7. Some children take 3 from 7 instead and write 4. That answer is wrong.
Taking away is not like adding. The order matters. 3 - 7 is not the same as 7 - 3. When the top is too small, you must borrow.
Read slowly and ask yourself one question: am I putting things together, or taking some away?
Words like left, sold, gave away and how many more mean take away.
A boat brings 82 fish from Lake Kivu. 45 fish are sold before lunch. How many fish are left?
82 - 45. Ones: 2 - 5, too small. Borrow: 7 tens and 12 ones.
Ones: 12 − 5 = 7. Tens: 7 − 4 = 3. Answer: 37 fish. Check: 37 + 45 = 82.
Keza has 90 Frw. She buys a sweet for 50 Frw. How much money is left?
90 - 50. Ones: 0 − 0 = 0. Tens: 9 − 5 = 4. No borrowing needed here.
Answer: 40 Frw.
Tip
Not enough ones? Knock next door. Borrow one ten, and it turns into ten more ones.
When you borrow, cross out the tens digit and write one less above it. That is the step children forget most, so do it first, before you take anything away.
Work each one out, then tap Show answer to check.
46 - 19 = ?
6 - 9 is too small. Borrow: 3 tens and 16 ones. Ones: 16 − 9 = 7. Tens: 3 − 1 = 2. Answer: 27. Check: 27 + 19 = 46.
75 - 28 = ?
Borrow: 6 tens and 15 ones. Ones: 15 − 8 = 7. Tens: 6 − 2 = 4. Answer: 47. Check: 47 + 28 = 75.
60 - 34 = ?
Borrow: 5 tens and 10 ones. Ones: 10 − 4 = 6. Tens: 5 − 3 = 2. Answer: 26. Check: 26 + 34 = 60.
93 - 7 = ?
The 7 is ones. Borrow: 8 tens and 13 ones. Ones: 13 − 7 = 6. The tens stay 8. Answer: 86. Check: 86 + 7 = 93.
Mugisha's class collected 71 bottle caps. They glued 36 of them onto a poster. How many caps are left?
71 - 36. Borrow: 6 tens and 11 ones. Ones: 11 − 6 = 5. Tens: 6 − 3 = 3. Answer: 35 caps. Check: 35 + 36 = 71.
What you learned today
Quick check
64 - 28. Can you take 8 from 4?
