Basic Mathematics

Finding the Missing Operations

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Finding the Missing Operations

Problems about number sentences leave out one item in the sentence and ask you to find the missing item.

In this lesson, you must find the missing sign of operation (+, −, ×, ÷) in each number sentence. The missing sign is shown as a box ( □).

What signs are needed to make the following number sentences true?

7 □ 2 = 5 Answer : 7 − 2 = 5
16 □ 4 = 4 Answer : 16 ÷ 4 = 4

Finding the Missing Operations

Click on the sign that belongs in the box.

4 □ 2 = 8

Question 1 of 8

4 ÷ 2 = 2, not 8. Try again.

4 × 2 = 8 is a true sentence.

4 + 2 = 6, not 8. Try again.

4 − 2 = 2, not 8. Try again.

One of these signs of operation makes the number sentence true. Try again.

Try each sign of operation until the number sentence is true.

Finding the Missing Operations

Click on the sign that belongs in the box.

111 □ 8 = 888

Question 2 of 8

111 + 8 = 119, not 888. Try again.

111 − 8 = 103, not 888. Try again.

111 × 8 = 888 is a true sentence.

111 ÷ 8 = 13 R7, not 888. Try again.

One of these signs of operation makes the number sentence true. Try again.

Try each sign of operation until the number sentence is true.

Finding the Missing Operations

Click on the sign that belongs in the box.

20 □ 4 = 12 × 2

Question 3 of 8

20 ÷ 4 = 5, not 24. Try again.

20 + 4 = 12 × 2 is a true sentence because both sides equal 24.

20 − 4 = 16, not 24. Try again.

20 × 4 = 80, not 24. Try again.

One of these signs of operation makes the number sentence true. Try again.

First, simplify the expression on the right: 12 × 2 = 24

Finding the Missing Operations

Click on the sign that belongs in the box.

2 × 3 □ 7 = 30 + 12

Question 4 of 8

2 × 3 × 7 = 30 + 12 is a true sentence because both sides equal 42.

2 × 3 ÷ 7 = 6 ÷ 7, and \(\color{#be0a0a}{\frac{6}{7}}\) is not equal to 42. Try again.

2 × 3 + 7 = 13, and 13 is not equal to 42. Try again.

2 × 3 − 7 = ⁻1, and ⁻1 is not equal to 42. Try again.

One of these signs of operation makes the number sentence true. Try again.

First, simplify the expression on the right:30 + 12 = 42

Finding the Missing Operations

Click on the number sentence in which the box should contain an addition sign (+).

Question 5 of 8

4 + 2 = 6 is a true sentence.

8 + 2 = 10, not 6. Try again.

3 + 2 = 5, not 6. Try again.

7 + 1 = 8, not 6. Try again.

One of these is a true addition sentence. Try again.

Add each expression on the left until the number sentence is true.

Finding the Missing Operations

Click on the number sentence in which the box should contain a division sign (÷).

Question 6 of 8

9 ÷ 3 = 3, not 6. Try again.

8 ÷ 4 = 2, not 32. Try again.

25 ÷ 5 = 5, not 20. Try again.

12 ÷ 4 = 3, not 8. Try again.

None of these is true as a division sentence.

Divide each expression on the left until the number sentence is true.

Finding the Missing Operations

Click on the number sentence in which the box should contain a subtraction sign (−).

Question 7 of 8

20 − 8 = 12, but 4 × 7 = 28. Try again.

50 − 10 = 40, but 25 ÷ 5 = 5. Try again.

5 − 9 = − 4, but 15 × 3 = 45. Try again.

40 − 8 = 8 × 4 is a true sentence because both sides equal 32.

One of these is a true subtraction sentence. Try again.

Subtract each expression on the left until the number sentence is true.

Finding the Missing Operations

Click on the number sentence in which the box should contain a multiplication sign (×).

Question 8 of 8

4 × 9 = 3 × 12 is a true sentence because both sides equal 36.

50 × 20 = 1000, but 7 × 10 = 70. Try again.

63 × 7 = 441, but 27 ÷ 3 = 9. Try again.

20 × 4 = 80, but 30 ÷ 6 = 5. Try again.

One of these is a true multiplication sentence. Try again.

Multiply each expression on the left until the number sentence is true.

Finding the Missing Operations