Question

Observe the following:

1 + 2 – 3 + 4 + 5 – 6 – 7 + 8 – 9 = -5 Change one ‘-‘ sign as ‘+’ sign to get the sum 9.

Answer 1

On observing the given expression, 1 + 2 – 3 + 4 + 5 – 6 – 7 + 8 – 9 = -5, we noticed that (-7) should be replaced by (+7) to get a result of 9.

Thus, 1 + 2 – 3 + 4 + 5 – 6 + 7 + 8 – 9

= (1 + 2 + 4 + 5 + 7 + 8) – (3 + 6 + 9)

= 27 – 18 

= 9