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?


Topics: Starter | Calculator

  • Transum,
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  • Don't miss the opportunity for your pupils to access the pupil interactive version of this activity if they have computers, iPads or other internet access devices. The link to the activity can be found in large type below making it easy for them to copy it from the projected image of this page.
    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.

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.
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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
1 × 4 × 5 = 20
1 × 5 × 4 = 20
4 × 1 × 5 = 20
4 × 5 × 1 = 20
5 × 1 × 4 = 20
5 × 4 × 1 = 20
2 × 2 × 5 = 20
2 × 5 × 2 = 20
5 × 2 × 2 = 20
8 × 5 ÷ 2 = 20
5 ÷ 2 × 8 = 20
3 × 4 + 8 = 20
2 × 6 + 8 = 20
2 × 7 + 6 = 20
3 × 5 + 5 = 20
2 × 8 + 4 = 20
4 × 4 + 4 = 20
2 × 9 + 2 = 20
3 × 6 + 2 = 20
4 × 5 + 0 = 20
4 × 3 + 8 = 20
6 × 2 + 8 = 20
7 × 2 + 6 = 20
5 × 3 + 5 = 20
8 × 2 + 4 = 20
9 × 2 + 2 = 20
6 × 3 + 2 = 20
5 × 4 + 0 = 20
8 + 3 × 4 = 20
8 + 2 × 6 = 20
6 + 2 × 7 = 20
5 + 3 × 5 = 20
4 + 2 × 8 = 20
4 + 4 × 4 = 20
2 + 2 × 9 = 20
2 + 3 × 6 = 20
0 + 4 × 5 = 20
8 + 4 × 3 = 20
8 + 6 × 2 = 20
6 + 7 × 2 = 20
5 + 5 × 3 = 20
4 + 8 × 2 = 20
2 + 9 × 2 = 20
2 + 6 × 3 = 20
0 + 5 × 4 = 20
4 × 5 − 0 = 20
7 × 3 − 1 = 20
6 × 4 − 4 = 20
5 × 5 − 5 = 20
3 × 9 − 7 = 20
4 × 7 − 8 = 20
5 × 4 − 0 = 20
3 × 7 − 1 = 20
4 × 6 − 4 = 20
9 × 3 − 7 = 20
7 × 4 − 8 = 20



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Teacher, do your students have access to computers such as tablets, iPads or Laptops?  This page was really designed for projection on a whiteboard but if you really want the students to have access to it here is a concise URL for a version of this page without the comments:

Transum.org/go/?Start=April21

However it would be better to assign one of the student interactive activities below.

Laptops In Lessons

Here is the URL which will take them to a related student activity.

Transum.org/go/?to=6keys

Student Activity

 


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