Six Keys

The challenge is to make 20 on your calculator using only six keys.

4 7 - 2 7 = 20
5 + 7 + 8 = 20
1 2 0 รท 6 = 20
            20

How many different ways can you do this? You could try making a different total. Is there a limit to the possible totals? What if you could use seven keys or five keys?


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Topics: Starter | Calculator

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    The pupil version records the solutions found by the pupils and they can copy and paste these solutions into their notes. The learning may be focussed on the number patterns and the sets of solutions found. The ultimate question of 'how many solutions are there?' should then become clearer.

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Previous Day | This starter is for 21 April | Next Day

 

Answers

30 − 10 = 20
31 − 11 = 20
32 − 12 = 20
33 − 13 = 20
34 − 14 = 20
35 − 15 = 20
36 − 16 = 20
37 − 17 = 20
38 − 18 = 20
39 − 19 = 20
40 − 20 = 20
41 − 21 = 20
42 − 22 = 20
43 − 23 = 20
44 − 24 = 20
45 − 25 = 20
46 − 26 = 20
47 − 27 = 20
48 − 28 = 20
49 − 29 = 20
50 − 30 = 20
51 − 31 = 20
52 − 32 = 20
53 − 33 = 20
54 − 34 = 20
55 − 35 = 20
56 − 36 = 20
57 − 37 = 20
58 − 38 = 20
59 − 39 = 20
60 − 40 = 20
61 − 41 = 20
62 − 42 = 20
63 − 43 = 20
64 − 44 = 20
65 − 45 = 20
66 − 46 = 20
67 − 47 = 20
68 − 48 = 20
69 − 49 = 20
70 − 50 = 20
71 − 51 = 20
72 − 52 = 20
73 − 53 = 20
74 − 54 = 20
75 − 55 = 20
76 − 56 = 20
77 − 57 = 20
78 − 58 = 20
79 − 59 = 20
80 − 60 = 20
81 − 61 = 20
82 − 62 = 20
83 − 63 = 20
84 − 64 = 20
85 − 65 = 20
86 − 66 = 20
87 − 67 = 20
88 − 68 = 20
89 − 69 = 20
90 − 70 = 20
91 − 71 = 20
92 − 72 = 20
93 − 73 = 20
94 − 74 = 20
95 − 75 = 20
96 − 76 = 20
97 − 77 = 20
98 − 78 = 20
99 − 79 = 20

10 + 10 = 20
100 ÷ 5 = 20
120 ÷ 6 = 20
140 ÷ 7 = 20
160 ÷ 8 = 20
180 ÷ 9 = 20



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