Missing number subtraction
The question
6 − ? = 1
6−?=1
6−?=1
6−1=5
6−5=1
- The gap is not at the end this time — the ANSWER is already there. What is missing is one of the two numbers going in, so the sum cannot just be worked left to right.
- 6 lost something and 1 was left, so what went is the difference between them: 6 − 1.
- Put it back in to be sure: 6 − 5 = 1. It holds, so the missing number is 5.
How it works.
- 01
The gap is not at the end this time — the ANSWER is already there. What is missing is one of the two numbers going in, so the sum cannot just be worked left to right.
- 02
6 lost something and 1 was left, so what went is the difference between them: 6 − 1.
- 03
Put it back in to be sure: 6 − 5 = 1. It holds, so the missing number is 5.