Problem 4
The purpose of the following flow-chart is to put a zero in each of the boxes: 5, 7, and 9.
In order to accomplish exactly this - no more and no less - what number must be in box 3?
Box No.
1 2 3 4 5 6 7 8 9 10 11 12
12 7 2 3 19 6 0 1 72 -3 9
START
1 Subtract: (number in box 12) - (number in box 12), put result into box 9.
2 Change Instruction 1: Decrease the last box-number mentioned in it, by 2.
no 3 Is the last box-number mentioned in Instruction 1 equal to (number in box 3)?
yes
END
What number must be in box 3?
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