To work out 68 − 25, take away the tens first: 68 − 20 = 48. Then take away the ones: 48 − 5 = 43.
When there are not enough ones, regroup. For 52 − 17, you cannot take 7 from 2, so swap one ten for ten ones. 52 becomes 4 tens and 12 ones. Now 12 − 7 = 5 and 4 tens − 1 ten = 3 tens. The answer is 35.
You can also count up from the smaller number. From 38 to 40 is 2, and from 40 to 73 is 33, so the difference is 35.
Worked example
73 − 38 =
- 73 − 30 = 43.
- 43 − 8 = 35.
Answer:35
Key words
- subtract
- take away
- difference
- the answer to a subtraction
- exchange
- change one ten into ten ones
Practise this
New questions every time.
Common Core-referenced: 2.NBT.B.5