A number decreased by 20% becomes 80. Find number.

Explanation

• A 20% decrease leaves 80% of the original number, so the equation is 0.8x = 80.
• Divide to solve: x = 80 ÷ 0.8 = 100.
• Check it: 20% of 100 is 20, and 100 − 20 = 80.
• Adding 20% to 80 gives 96, not 100, because the percentage must be taken from the original number.
• Percentage decrease MCQs in FPSC and PPSC papers follow this same 0.8x pattern, so writing the equation first is the safest step.