Missing Numbers in Subtraction—Let's Practise!

Missing Numbers in Subtraction—Let's Practise! exercise

• What's the missing number?

  Hints

  To rewrite the equation, swap 32 with the missing number.

  To find the missing number, solve 45 - 32.

  Solution

  45 - ? = 32

  45 - 32 = ?

  45 - 32 = 13. 13 is the missing number.

  Check your work. Put 13 back into the original equation. 45 - 13 = 32.

• Find the missing number.

  Hints

  Rewrite the equation.

  • Swap the missing number with 16.

  • When the missing number is first in the original equation, change the operation sign to +.

  Solve the new equation

  • What is 16 + 21?

  • Put the answer into the original equation to check your work.

  Solution

  The missing number is 37.

  • Rewrite the equation as 16 + 21 = ?

  • Solve the new equation by adding 16 + 21 = 37.

  • Check your work. Put the missing number, 37, into the original equation. 37 - 21 = 16.

• Find the missing numbers.

  Hints

  Step 1: Rewrite the equation.

  Swap the missing number with the number to the right of the equals sign.

  So, 46 - ? = 16 should be rewritten as 46 - 16 = ?

  Step 2: Solve the new equation. What is 46 - 16?

  The image below shows 46 blue dots. 16 are inside a red box.

  Count the number of blue dots outside of the red box to solve the equation.

  Step 3: Check your work.

  When you've found the answer, put it into the original equation: 46 - ? = 16.

  If you subtract the correct number from 46, you will get 16!

  Solution

  1. 46 - 30 = 16. The missing number is 30.

  • Rewrite the equation as 46 - 16 = ?
  • Subtract. 46 - 16 = 30.

  2. 59 - 26 = 33. The missing number is 26.

  • Rewrite the equation as 59 - 33 = ?
  • Subtract. 59 - 33 = 26.

  3. 80 - 11 = 69. The missing number is 11.

  • Rewrite the equation as 80 - 69 = ?
  • Subtract. 80 - 69 = 11.

• Find all of the missing numbers.

  Hints

  Step one: rewrite the equation.

  Rewrite the equation so that the missing number is on the right of the equals sign.

  In this problem, the missing number is first in the original equation. This is shown by the red box in the image below.

  • When the missing number is first, make sure to rewrite your equation with a +.

  • The rewritten equation will be 12 + 45 = ?

  In this problem, the missing number is second.

  • When the missing number is second, do not change the operation sign.

  • Swap the numbers as shown in the image. The new equation will be 78 - 15 = ?

  Solution

  ? - 45 = 12. The missing number is 57.

  • Rewrite the equation as 12 + 45 = ?
  • Add 12 + 45 = 57.
  • Check your work. Put 57 into the original equation. 57 - 45 = 12

  ? - 43 = 9. The missing number is 52.

  • Rewrite the equation as 43 + 9 = ?
  • Add 43 + 9 = 52.
  • Check your work. Put 52 into the original equation. 52 - 43 = 9

  78 - ? = 15. The missing number is 63.

  • Rewrite the equation as 78 - 15 = ?
  • Subtract 78 - 15 = 63.
  • Check your work. Put 63 into the original equation. 78 - 63 = 15

  ? - 67 = 18. The missing number is 85.

  • Rewrite the equation as 67 + 18 = ?
  • Add 67 + 18 = 85.
  • Check your work. Put 85 into the original equation. 85 - 67 = 18

• What's the missing number?

  Hints

  First, rewrite the equation so that the missing number is on the right of the = . This is done for you in the image.

  Solve the new equation: 51 - 37 = ?

  What is 51 - 37?

  This image shows 51 blue dots. 37 dots are in the red box.

  Count the number of dots outside of the red box to find 51 - 37.

  Solution

  51 - 37 = 14

  Put 14 into the original equation to check your work:

  51 - 14 = 37.

• Solve the word problem.

  Hints

  We can write this problem as a subtraction equation.

  The number of sweets Razzi started with (70) - the sweets Razzi ate (?) = the number of sweets Razzi has left (49).

  Next, rewrite the equation so that the missing number is on the right of the equals sign.

  Solve the rewritten equation. The answer tells you how many sweets Razzi ate!

  Plug it back into the original equation to check your work.

  Solution

  Razzi ate 21 sweets.

  Step 1: Write the original equation

  • The original equation should be written as 70 - ? = 49.

  Step 2: Rewrite the equation

  • Rewrite the equation as 70 - 49 = ?

  Step 3: Solve the new equation

  • 70 - 49 = 21.

  Step 4: Check your work

  • Put 21 into the original equation. 70 - 21 = 49