Correct Placement of Subtraction Operator
This was the question!
For a moment. let's put '+' operator in all given boxes.
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 33.
Let 'x' be the number ahead of which '-' should be there where x can be any number from 1 to 9.
In above addition the x is already (unknown value) added so first we need to subtract it twice from LHS; first to compensate the addition operation & second for the mandatory subtraction operator that is to be placed at right place.
So for example, if it's ahead of 4 as right place then
1 + 2 + 3 + 4 - 4 - 4 + 5 + 6 + 7 + 8 + 9 = 33.
1 + 2 + 3 + (4 - 4) - 4 + 5 + 6 + 7 + 8 + 9 = 33.
For x, which is already there & can be any from 1 to 9,
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 - x - x = 33.
45 - 2x = 33
2x = 12
x = 6.
Hence, the subtraction (-) sign should be ahead of 6.
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