Basic Mathematics

Missing Numbers in Related Number Sentences

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Missing Numbers in Related Number Sentences
Addition and subtraction are inverse operations.

For example, adding 7 to a number and then subtracting 7 does not change the number.

Multiplication and division are also inverse operations.


Missing Numbers in Related Number Sentences
The number sentence, 4 + 2= 6,
is related to 6 − 4= 2,
and 6 − 2= 4,
because the inverse operation for addition is subtraction.
In this lesson, we say that the three number sentences are related by inverse operations.
The same relationship holds for multiplication and division.
The number sentence,  4 × 2= 8,
is related to  8 ÷ 4= 2,
and  8 ÷ 2= 4,
Missing Numbers in Related Number Sentences
What number belongs in the box to make the second number sentence true?
21 = 3 × 7
3 = 21 ÷ □
No calculations are necessary. Notice that the two number sentences are related by inverse operations. Therefore, they use the same three numbers. The missing number is 7.
Missing Numbers in Related Number Sentences
Click on the number that belongs in the box.
9 + 7 = 16 16 − ⃞ = 9
  7
16
  9
25
None of these
Question 1 of 8
16 − 7 = 9 is related to the number sentence 9 + 7 = 16.
16 − 16 = 0, not 9. Try again.
16 − 9 = 7, not 9. Try again.
16 − 25 = −9, not 9. Try again.
One of these makes a true number sentence. Try again.
The two number sentences are related by inverse operations.
Missing Numbers in Related Number Sentences
Click on the number that belongs in the box.
7 × 4 = 28 28 ÷ ⃞ = 4
    4
  28
112
    7
None of these
Question 2 of 8
28 ÷ 4 = 7, not 4. Try again.
28 ÷ 28 = 1, not 4. Try again.
28 ÷ 112 is less than 1. 28 ÷ 112 is not equal to 4. Try again.
28 ÷ 7 = 4 is related to the number sentence 7 × 4 = 28.
One of these makes a true number sentence. Try again.
The two number sentences are related by inverse operations.
Missing Numbers in Related Number Sentences
Click on the number sentence that is not related to the others.
8 − 5 = 3
5 + 3 = 8
8 = 4 + 4
5 = 8 − 3
None of these
Question 3 of 8
The inverse of this is 3 + 5 = 8. It is related to two of the other number sentences. Try again.
The inverse of this is 8 − 3 = 5. It is related to two of the other number sentences. Try again.
8 = 4 + 4 is not related to the other number sentences because the addends are different.
The inverse of this is 5 + 3 = 8. It is related to two of the other number sentences. Try again.
One of these number sentences has different addends from the others. Try again.
Number sentences are related when they use the same numbers in inverse operations.
Missing Numbers in Related Number Sentences
Click on the number sentence that is not related to the others.
3 + 4 = 7
3 × 4 = 12
12 ÷ 3 = 4
3 = 12 ÷ 4
None of these
Question 4 of 8
3 + 4 = 7 is not related to the other number sentences because it's an addition sentence.
The inverse of this is 12 ÷ 4 = 3. It is related to two of the other number sentences. Try again.
The inverse of this is 4 × 3 = 12. It is related to two of the other number sentences. Try again.
The inverse of this is 3 × 4 = 12. It is related to two of the other number sentences. Try again.
One of these number sentences uses an operation that is not division and not the inverse of division. Try again.
Multiplication and division are inverse operations.
Missing Numbers in Related Number Sentences
Click on the number that belongs in both boxes.
77 − 22 = ⃞ ⃞ + 22 = 77
55
22
77
99
None of these
Question 5 of 8
77 − 22 = 55 and 55 + 22 = 77 are both true number sentences.
77 − 22 = 22 and 22 + 22 = 77 are not true sentences. Try again.
77 − 22 = 77 and 77 + 22 = 77 are not true sentences. Try again.
77 − 22 = 99 and 99 + 22 = 77 are not true sentences. Try again.
One of these numbers makes both number sentences true. Try again.
These are related number sentences. Find the missing number in either equation.
Missing Numbers in Related Number Sentences
Click on the number that belongs in both boxes.
6 × 9 = ⃞ ⃞ ÷ 6 = 9
69
54
15
18
None of these
Question 6 of 8
6 × 9 = 69 and 69 ÷ 6 = 9 are not true sentences. Try again.
6 × 9 = 54 and 54 ÷ 6 = 9 are both true number sentences.
6 × 9 = 15 and 15 ÷ 6 = 9 are not true sentences. Try again.
6 × 9 = 18 and 18 ÷ 6 = 9 are not true sentences. Try again.
One of these numbers makes both number sentences true. Try again.
These are related number sentences. Find the missing number in either equation.
Missing Numbers in Related Number Sentences
Click on the number sentence that is not related to the others.
11 − 6 = 5
6 + 5 = 11
30 ÷ 6 = 5
6 = 11 − 5
None of these
Question 7 of 8
The inverse of this is 5 + 6 = 11. It is related to two of the other number sentences. Try again.
The inverse of this is 11 − 5 = 6. It is related to two of the other number sentences. Try again.
30 ÷ 6 = 5 is not related to the other number sentences because it is a division sentence.
The inverse of this is 6 + 5 = 11. It is related to two of the other number sentences. Try again.
One of these number sentences uses an operation that is not subtraction and not the inverse of subtraction. Try again.
Addition and subtraction are inverse operations.
Missing Numbers in Related Number Sentences
Click on the number sentence that is not related to the others.
30 ÷ 2 = 15
15 × 2 = 30
17 − 2 = 15
30 ÷ 15 = 2
None of these
Question 8 of 8
The inverse of this is 15 × 2 = 30. It is related to two of the other number sentences. Try again.
The inverse of this is 30 ÷ 2 = 15. It is related to two of the other number sentences. Try again.
17 − 2 = 15 is not related to the others because it's a subtraction sentence.
The inverse of this is 2 × 15 = 30. It is related to two of the other number sentences. Try again.
One of these number sentences uses an operation that is not division and not the inverse of division. Try again.
Multiplication and division are inverse operations.
Missing Numbers in Related Number Sentences