← Change Exercise
Think of a number — work backwards
These steps were done to a number. What was the starting number?
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Correct
When you know the result and all the steps, you can find the starting number by working backwards. Start at the end and replace each step with its inverse: instead of + 25 subtract 25, instead of × 3 divide by 3.
What does this generator do?
It shows a chain of two to four steps with addition, subtraction, multiplication and division. You only know the result at the end and look for the number at the start.
How to use it
1) Start from the result at the end of the chain. 2) Go back along the arrows and undo each step. 3) Put your number at the start and check that the chain works.