# Explain and check solutions to problems, including by using the inverse operation

 1 Make 20: 7+4+? 2 Make 20: 11+5+? 3 Make 20: 8+9+? 4 Add Board: *0 + 20 = 100 5 Make 50: 20+10+? 6 Make 50: 20+10+? 7 Make 50: 20+10+? 8 Make 50: 20+10+? 9 Make 50: 20+10+? 10 Make 30: 10 + 11 + ? = 30 11 Make 50: 20+10+? 12 Make 30: 19 + 2 + ? = 30 13 Make 30: 20 + 10 + ? = 30 14 Make 30: 16 + 4 + ? = 30 15 Make 30: 18 + 3 + ? = 30 16 Make 50: 40 + 4 + ? 17 Make 36: 20 + 14 + ? 18 Make 39: 30 + 6 + ? 19 Make 37: 12 + 20 + 5 20 Make 34: 10 + 22 + ? 21 Make 50: 39+7+? = 50 22 Make 50: 39+5+? = 50 23 Make 50: 35+5+? = 50 24 Make 50: 38+10+? = 50 25 Make 50: 42+6+? = 50 26 Number detectives 45+*=100 27 Number detectives 75+*=100 28 Number detectives 85+*=100 29 Number detectives 35+*=100 30 Number detectives 5+*=100 31 Add board 5* + 46 = *8 32 Add board 35 + *3 = 7* 33 Make 200: 130+50+* 34 Make 200: 70+100+* 35 Make 200: 60+40+* 36 Make 200: 90+30+* 37 Make 200: 150+40+* 38 On the Board 45 + 3* = *7 39 On the Board 3* + *5 = 98 40 On the Board 4* + 42 = *9 41 On the Board 3* + 62 = *6 42 On the Board 8* + *6 = 98 43 On the Board 33 + *5 = 7* 44 On the Board *8 + 51 = 7* 45 On the Board: *52+10*=3*8 46 On the Board: *8*+91=*78 47 On the Board: *46+*2=43* 48 On the Board: *6*+73=5*6 49 Make 100: 50, 20 & ? 50 Make 100: 60, 20 & ? 51 Make 100: 10, 40 & ? 52 Make 100: 10, 30 & ? 53 Make 100: 60, 40 & ? 54 On the Board: *4+7*=100 55 On the Board: *4+3*=100 56 Hundreds and hundreds: 42?+3?8=79? 57 Hundreds and hundreds: 17?+?23=2?7 58 Ball skills: How many more to make 10? 7+2+? 59 Ball skills: How many more to make 10? 6+3+? 60 Ball skills: How many more to make 10? 5+3+? 61 Ball skills: How many more to make 10? 7+1+? 62 Ball skills: How many more to make 10? 2+3+? 63 Write the missing number: 15 + 1 + ? = 20 64 Write the missing number: ? + 11 + 2 = 20 65 Write the missing number: 3 + 4 + ? = 20 66 Write the missing number: ? + 5 + 6 = 20 67 Write the missing number: 5 + 8 + ? = 20 68 Write the missing number: 4 + 8 + ? = 20 69 Write the missing number: 11 + ? + 2 = 20 70 Write the missing number: ? + 13 + 4 = 20 71 Write the missing number: 6 + 9 + ? = 20 72 Write the missing number: 4 + ? + 6 = 20 73 Write the missing number: 8 + ? + 7 = 20 74 Write the missing number: 6 + ? + 8 = 20 75 Write the missing number: ? + 9 + 6 = 20 76 Write the missing number: 2 + 11 = ? = 20 77 Write the missing number: ? + 7 + 9 = 20 78 Takeaway board: 17-?=11 79 Takeaway board: 15-?=11 80 Takeaway board: 18-? = 12 81 Takeaway board: 16-? = 13 82 Takeaway board: 19-? = 14 83 Put in the missing number: 5 + 4 + ? = 16 84 Put in the missing number: 11 + ? + 6 = 25 85 Write in the missing number: ? + 13 + 5 = 21 86 Put in the missing number: 9 + 2 + ? = 19 87 Put in the missing number: ? + 10 + 14 = 28 88 Write the missing number: 20 + 3 + ? = 30 89 Write the missing number: 12 + ? + 10 = 30 90 Write the missing number: 15 + ? + 5 = 30 91 Write the missing number: 9 + ? + 12 = 30 92 Write the missing number: ? + 5 + 4 = 30 93 Write the missing number: 15 + ? + 6 = 30 94 Write the missing number: 18 + ? + 2 = 30 95 Write the missing number: 20 + 3 + ? = 30 96 Write the missing number: ? + 13 + 5 = 30 97 Write the missing number: 14 + 7 + ? = 30 98 Takeaway board: 3? - 14 = 23 99 Takeaway board: 2? - 13 = 13 100 Takeaway board: 4? - 22 = 27 101 Takeaway board: 6? - 12 = 55 102 Takeaway board: 5? - 26 = 32 103 Write the missing number: 7 + ? + 14 = 30 104 Write the missing number: 15 + 4 + ? = 30 105 Write the missing number: 12 + 10 + ? = 30 106 Write the missing number: 15 + 5 + ? = 30 107 Write the missing number: 18 + 8 + ? = 30 108 Write the missing number: 5 + 5 + ? = 30 109 Takeaway board 152-? = 144 110 Takeaway board 547-? = 538 111 Takeaway board 553-? = 546 112 Takeaway board 291-? 285 113 Takeaway board 742-? = 737 114 Takeaway Board ?9-18 = 71 115 Takeaway Board 67-1?=53 116 Takeaway Board 79-?8=61 117 Takeaway Board ?7-17=50 118 Takeaway Board ?3-21=72 119 Write the missing number: 25 + 3 + ? = 35 120 Write the missing number: 25 + 4 + ? = 35 121 Write the missing number: 25 + 2 + ? = 35 122 Write the missing number: 25 + 5 + ? = 35 123 Write the missing number: 25 + 1 + ? = 35 124 Write the missing number: 35 + 5 + ? = 50 125 Write the missing number: 35 + 7 + ? = 50 126 Write the missing number: 35 + 9 + ? = 50 127 Write the missing number: 35 + 13 + ? = 50 128 Write the missing number: 35 + 11 + ? = 50 129 Hundreds takeaway 350-**=330 130 Hundreds takeaway 697-**=614 131 Hundreds takeaway 457-**=425 132 Hundreds takeaway 596-**=543 133 Hundreds takeaway 875-**=865 134 Hundreds takeaway 997-**=971 135 Hundreds Takeaway: 6*2-32* = *21 136 Hundreds Takeaway: **2-43*=362 137 Hundreds Takeaway: *1*-5*4=414 138 Hundreds Takeaway: *8*-2*2=132 139 Hundreds Takeaway: 5*9-35*=*11 140 Sum In A Circle - numbers in each groups total 15 141 Sum In A Circle - numbers in each group total 15 142 16 go to WaterWorld: 5+4+3+? 143 17 go to Waterworld: 6+5+2+? 144 14 go to Waterworld: 6+3+2+? 145 18 go to WaterWorld: 3+3+2+? 146 15 go to WaterWorld: 5+3+2+? 147 16 go to Waterworld? 2+3+3+? 148 19 go to Waterworld: 5+4+3+? 149 Make 50: 32+8+? = 50