Missing Numbers in Subtraction—Let's Practice!
Basics on the topic Missing Numbers in Subtraction—Let's Practice!
Today we are solving missing numbers in subtraction problems with Razzi! This video contains examples to help you further practice and grow confident in this topic.
Transcript Missing Numbers in Subtraction—Let's Practice!
Razzi says get these items ready (...) Because today we're going to practice... Missing Numbers in Subtraction. It's time to begin! Find the missing number in the number sentence... seventyeight minus blank equals twentyone. Rewrite the number sentence by moving twentyone BEFORE the equal sign. Then solve seventyeight minus twentyone which equals fiftyseven. Check your answer by putting fiftyseven in the ORIGINAL number sentence. Did you also get seventyeight minus fiftyseven equals twentyone? Let's tackle the next problem! Ninetythree minus blank equals ten. Rewrite the number sentence by moving ten BEFORE the equal sign. Then solve ninetythree minus ten which equals eightythree. Check your answer by putting eightythree in the ORIGINAL number sentence. Did you also get ninetythree minus eightythree equals ten? Let's try another! Blank minus twentytwo equals fiftyfive. Since the first number is missing in the subtraction sentence, rewrite the number sentence as twentytwo PLUS fiftyfive... then solve to get seventyseven. Check your answer by putting seventyseven in the ORIGINAL number sentence. Did you also get seventyseven minus twentytwo equals fiftyfive? Let's try one more! Blank minus eightynine equals two. Rewrite the number sentence as eightynine PLUS two... then solve to get ninetyone. Check your answer by putting ninetyone in the ORIGINAL number sentence. Did you also get ninetyone minus eightynine equals two? Razzi had so much fun practicing with you today! See you next time!
Missing Numbers in Subtraction—Let's Practice! exercise

Rewrite the problem without missing numbers and solve.
HintsTo rewrite the equation, swap 32 with the missing number.
To find the missing number, solve 45  32.
SolutionThe equation without missing numbers is 45  32 = ?.
Solve 45  32 = 13. 13 is the missing number.
Check your work. Plug 13 back into the original equation 45  13 = 32.

Solve for the missing number.
HintsRewrite 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?
 Plug the answer into the original equation to check your work.
SolutionThe missing number is 37.
 Rewrite the equation as 16 + 21 = ?.
 Solve the new equation by adding 16 + 21 = 37.
 Check your work. Plug the missing number, 37, into the original equation. 37  21 = 16.

Find the missing numbers.
HintsStep 1: Rewrite the equation.
Swap the missing number with the number to the right of the equal 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, plug it into the original equation: 46  ? = 16.
If you subtract the correct number from 46, you will get 16!
Solution 46  30 = 16. The missing number is 30.
 Rewrite the equation as 46  16 = ?.
 Subtract. 46  16 = 30.
 Rewrite the equation as 59  33 = ?.
 Subtract. 59  33 = 26.
 Rewrite the equation as 80  69 = ?.
 Subtract. 80  69 = 11.

Find all the missing numbers.
HintsStep one: rewrite the equation
Rewrite the equation so that the missing number is on the right of the equal 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. Plug 57 into the original equation. Does 57  45 = 12? YES!
 Rewrite the equation as 43 + 9 = ?.
 Add 43 + 9 = 52.
 Check your work. Plug 52 into the original equation. Does 52  43 = 9? YES!
 Rewrite the equation as 78  15 = ?.
 Subtract 78  15 = 63.
 Check your work. Plug 63 into the original equation. Does 78  63 = 15? YES!

What's the missing number?
HintsFirst, 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.
Solution51  37 = 14.
Plug 14 into the original equation to check your work:
51  14 = 37.

Solve the word problem.
HintsWe can write this problem as a subtraction equation. It is shown below.
The number of candies Razzi started with (70)  the candies Razzi ate (?) = the number of candies Razzi has left (49).
Next, rewrite the equation so that the missing number is on the right of the equal sign.
The rewritten equation is shown below.
Solve the rewritten equation. The answer tells you how many candies Razzi ate!
Plug it back into the original equation to check your work.
SolutionRazzi ate 21 pieces of candy.
Step 1: Write the original equation
 The original equation should be written as 70  ? = 49.
 Rewrite the equation as 70  49 = ?.
 70  49 = 21.
 Plug 21 into the original equation. Does 70  21 = 49? YES!
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