 15 - 5 = 10, so 10 + 5 = 15!

# Year 2 Calculation - Addition to Check Subtraction

This quiz addresses the requirements of the National Curriculum KS1 Maths and Numeracy for children aged 6 and 7 in year 2. Specifically this quiz is aimed at the section dealing with counting on from any given number.

Recognising that addition is the inverse, or opposite, of subtraction is useful when it comes to checking answers. For example, realising that 13 - 8 = 5 could be checked by adding 8 + 5 to give 13 means that subtraction calculation answers can be accurately checked.

Question 1
Which calculation could you use to check that 23 - 6 = 17 is correct?
6 + 17
23 + 7
23 + 6 + 7
23 + 6 + 7
If adding the two smaller numbers does not give the larger number as their total, something has gone wrong!
Question 2
Check 67 - 25 = 42 with addition. Is this calculation correct?
Incorrect answer: 25 + 67 = 92
Correct answer: 25 - 67 = 42
Incorrect answer: 67 + 42 = 109
Correct answer: 25 + 42 = 67
The two smaller numbers add to give 67
Question 3
Why is 33 - 20 = 13 true?
Because the sum of all three numbers gives the same answer
Because 13 subtracted from 20 is 33
Because the total of 13 and 33 is 20
Because 20 + 13 = 33
If you had 33 pennies and took 20 away (leaving 13), putting them all back again (13 + 20) would result in 33 pennies again
Question 4
Which calculation proves this calculation is incorrect?
76 - 34 = 45
76 - 45 = 34
45 - 34 = 11
34 + 45 = 79
34 + 45 = 76
The two smaller numbers do not add to total the larger one
Question 5
Which calculation proves this calculation is incorrect?
62 - 19 = 55
55 + 19 = 62
55 + 19 = 74
62 + 19 = 55
62 + 55 = 19
The two smaller numbers do not add to total the larger one
Question 6
Which calculation could you use to check that 18 - 7 = 11 is correct?
11 + 18
7 + 18
7 + 11
11 + 7 + 18
Adding the two smaller numbers should total the larger number
Question 7
Which calculation shows that this subtraction is correct?
78 - 40 = 38
40 + 78 = 38
40 - 38 = 78
38 + 78 = 40
38 + 10 + 10 + 10 + 10 = 78
Adding 4 groups of 10 to 38 gives the starting number of 78
Question 8
How could you check that 24 - 8 = 16?
By checking that 16 + 8 = 24
By checking the total of all three numbers
By finding the difference between 16 and 8
By finding the total of 24 and 8
Adding the two smaller numbers should give the larger one
Question 9
Check 84 - 21 = 73 with addition. Is this calculation correct?
Correct answer: 73 + 21 = 84
Incorrect answer: 73 + 21 = 94
Incorrect answer: 84 + 21 = 105
Incorrect answer: 84 + 73 = 157
The two smaller numbers do not add to give the larger number, so the original calculation is incorrect
Question 10
Why is 48 - 20 = 54 incorrect?
Because 48 is more than 20
Because the numbers are all even
Because 20 + 54 = 74, not 48
Because the total of all three numbers is 122
The answer to a subtraction cannot be larger than the number at the beginning! 