Three-digit adding and taking away · Usually met around P2
Taking away twice
Left to right, or take away the two numbers' sum.
How to do it
Method
Left to right, or take away the two numbers' sum
85 − 27 − 9 = 58 − 9 = 49
Another way
Take away the sum
500 − 136 − 64 = 500 − 200 = 300
In full
Take away from left to right: 85 − 27 − 9, first 85 − 27 = 58, then 58 − 9 = 49. When a column is too small, borrow 1 from the place before as 10. Taking away two numbers one after the other is the same as taking away their sum: 500 − 136 − 64 = 500 − (136 + 64) = 500 − 200 = 300, handy when the two make a whole hundred. Or take away the easier one first: the answer is the same.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
657 − 276 − 70 = □
Show the answer and working
Answer: 311
Left to right: 657 − 276 = 381, 381 − 70 = 311.
Example 2
303 − 188 − 18 = 303 − 170
True or false?
Show the answer and working
Answer: False
Taking away 188 and then 18 is taking away their sum, 188 + 18, at once.
Example 3
655 − 126 − 74 = □
Show the answer and working
Answer: 455
126 and 74 make 200, so 655 − 200 = 455.
Practise it in the game →Three-digit adding and taking away · Free to start, unlimited questions, no download