This handy Spectrum Math Grade 4 Answer Key Chapter 1 Lesson 1.7 Thinking Subtraction for Addition provides detailed answers for the workbook questions. Question 1.
a.  Explanation:
By adding 47 to 32 we will get 79
32 + 47 = 79
By subtracting 47 from 79 we will get 32
79 – 47 = 32
Both the numbers are same.

b.  Explanation:
By adding 19 to 63 we will get 82
63 + 19 = 82
By subtracting 19 from 82 we will get 63
82 – 19 = 63
Both the numbers are same.

c.  Explanation:
By adding 24 to 38 we will get 62
38 + 24 = 62
By subtracting 24 from 62 we will get 38
62 – 24 = 38
Both the numbers are same.

d.  Explanation:
By adding 47 to 52 we will get 99
52 + 47 = 99
By subtracting 47 from 99 we will get 52
99 – 47 = 52
Both the numbers are same.

e.  Explanation:
By adding 15 to 28 we will get 43
28 + 15 = 43
By subtracting 15 from 43 we will get 28
43 – 15 = 28
Both the numbers are same.

f.  Explanation:
By adding 15 to 75 we will get 90
75 + 15 = 90
By subtracting 15 from 90 we will get 75
90 – 15 = 75
Both the numbers are same.

Question 2.
a.  Explanation:
By adding 27 to 48 we will get 75
48 + 27 =75
By subtracting 27 from 75 we will get 48
75 – 27 = 48
Both the numbers are same.

b.  Explanation:
By adding 10 to 82 we will get 92
82 + 10 = 92
By subtracting 10 from 92 we will get 82
92 – 10 = 82
Both the numbers are same.

c.  Explanation:
By adding 38 to 56 we will get 94
56 + 38 = 94
By subtracting 38 from 94 we will get 56
94 – 38 = 56
Both the numbers are same.

d.  Explanation:
By adding 27 to 44 we will get 71
44 + 27 = 71
By subtracting 27 from 71 we will get 44
71 – 27 = 44
Both the numbers are same.

e.  Explanation:
By adding 27 to 28 we will get 55
28 + 27 = 55
By subtracting 27 from 55 we will get 28
55 – 27 = 28
Both the numbers are same.

f.  Explanation:
By adding 32 to 39 we will get 71
39 + 32 = 71
By subtracting 32 from 71 we will get 39
71 – 32 = 39
Both the numbers are same.

Question 3.
a.  Explanation:
By adding 59 to 31 we will get 90
31 + 59 = 90
By subtracting 59 from 90 we will get 31
90 – 59 = 31
Both the numbers are same.

b.  Explanation:
By adding 18 to 43 we will get 61
43 + 18 = 61
By subtracting 18 from 61 we will get 43
61 – 18 = 43
Both the numbers are same.

c.  Explanation:
By adding 29 to 61 we will get 90
61 + 29 = 90
By subtracting 29 from 90 we will get 61
90 – 29 = 61
Both the numbers are same.

d.  Explanation:
By adding 17 to 125 we will get 142
125 + 17 = 142
By subtracting 17 from 142 we will get 125
142 – 17 = 125
Both the numbers are same.

e.  Explanation:
By adding 38 to 155 we will get 193
155 + 38 = 193
By subtracting 38 from 193 we will get 155
193 – 38 = 155
Both the numbers are same.

f.  Explanation:
By adding 69 to 205 we will get 274
205 + 69 = 274
By subtracting 69 from 274 we will get 205
274 – 69 = 205
Both the numbers are same.

Question 4.
a.  Explanation:
By adding 14 to 199 we will get 213
199 + 14 =213
By subtracting 14 from 213 we will get 199
213 – 14 =199
Both the numbers are same.

b.  Explanation:
By adding 33 to 128 we will get 161
128 + 33 = 161
By subtracting 33 from 161 we will get 128
161 – 33 = 128
Both the numbers are same.

c.  Explanation:
By adding 50 to 125 we will get 175
125 + 50 = 175
By subtracting 50 from 175 we will get 125
175 – 50 = 125
Both the numbers are same.

d.  Explanation:
By adding 32 to 109 we will get 141
109 + 32 = 141
By subtracting 32 from 141 we will get 109
141 – 32 = 109
Both the numbers are same.

e.  Explanation:
By adding 27 to 155 we will get 182
155 + 27 = 182
By subtracting 27 from 182 we will get 155
182 – 27 = 155
Both the numbers are same.

f.  