# 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 ÷ 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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• 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.

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 30 − 10 = 2031 − 11 = 2032 − 12 = 2033 − 13 = 2034 − 14 = 2035 − 15 = 2036 − 16 = 2037 − 17 = 2038 − 18 = 2039 − 19 = 2040 − 20 = 2041 − 21 = 2042 − 22 = 2043 − 23 = 2044 − 24 = 2045 − 25 = 2046 − 26 = 2047 − 27 = 2048 − 28 = 2049 − 29 = 2050 − 30 = 2051 − 31 = 2052 − 32 = 2053 − 33 = 2054 − 34 = 2055 − 35 = 2056 − 36 = 2057 − 37 = 2058 − 38 = 2059 − 39 = 2060 − 40 = 2061 − 41 = 2062 − 42 = 2063 − 43 = 2064 − 44 = 2065 − 45 = 2066 − 46 = 2067 − 47 = 2068 − 48 = 2069 − 49 = 2070 − 50 = 2071 − 51 = 2072 − 52 = 2073 − 53 = 2074 − 54 = 2075 − 55 = 2076 − 56 = 2077 − 57 = 2078 − 58 = 2079 − 59 = 2080 − 60 = 2081 − 61 = 2082 − 62 = 2083 − 63 = 2084 − 64 = 2085 − 65 = 2086 − 66 = 2087 − 67 = 2088 − 68 = 2089 − 69 = 2090 − 70 = 2091 − 71 = 2092 − 72 = 2093 − 73 = 2094 − 74 = 2095 − 75 = 2096 − 76 = 2097 − 77 = 2098 − 78 = 2099 − 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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This book is targeted at the Higher tier GCSE, and provides a wealth of practice with careful progression, alongside substantial revision support for the new-style grading and exam questions. With all the new topics included, and a dedicated section on using and applying mathematics, this unique resource can be used either as a course book over two or three years or as a revision text in the run-up to exams. more...   Teacher, do your students have access to computers?Do they have iPads or Laptops in Lessons? Whether your students each have a TabletPC, a Surface or a Mac, this activity lends itself to eLearning (Engaged Learning). Transum.org/go/?Start=April21

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

Transum.org/go/?to=6keys  For All: