Question

A number is first increased by 20℅ and then decreased by 15℅ find the net increase or decrease.Does it make any difference if it 15℅ first and then 20% increased?

Answer 1

Let the original number be 'x'.

• The number is first increased by 20%:

        Therefore, new number = x + 0.2x = 1.2x

• It is then decreased by 15%:

       Therefore, the new number = (1.2x) - 0.15(1.2x) = 1.02x

Therefore, the net is an increase by 2%.

Now for the second part of the question:

• If the number is first decreased by 15%:

       Therefore, the new number = x - 0.15x = 0.85x

• It is then increased by 20%:

       Therefore, the new number = 0.85x + 0.2(0.85x) = 1.02x

Therefore, swapping the order has no difference.