Using Nine Digits To Get 100
Activities
Now write out the nine digits: 1 2 3 4 5 6 7 8 9.
You can as in the previous game arrive at 100 by inserting a plus or minus six times and get 100 thus:
12 + 3 - 4 + 5 + 67 + 8 + 9 = 100.
If you want to use only four plus or minus signs, you proceed thus:
123 + 4 - 5 + 67 - 89 = 100.
Now try and obtain 100 using only three plus or minus signs. It's much more difficult but possible.
Solution
123 - 45 - 67 + 89 = 100
This is the only solution. It's impossible to arrive at the same result by using the plus and minus signs less than three times
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Source: Numeracy Counts !, Anita Rampal, R Ramanujam and L S Saraswati, N L R C, LBS National Academy of Administration, Mussoorie. |