Question 1

The price of a mobile phone decreased by 20% in the first month and then increased by 25% in the second month. If the final price is ₹12,000, what was the original price?

Accepted Answer

Step 1: Let the original price be P. After a 20% decrease, the price becomes 0.80P. Step 2: After a 25% increase on 0.80P, the price becomes 0.80P × 1.25 = 1.00P. Step 3: We are told the final price is ₹12,000, so 1.00P = 12,000. Step 4: Therefore, P = ₹12,000. Therefore, answer is C.

Question 2

The price of a commodity increases by 20% in the first year. In the second year, the price decreases by 10%. What is the net percentage change in the price over the two years?

Accepted Answer

Step 1: Let the initial price be ₹100. Step 2: After 20% increase in year 1: Price = 100 + (20% of 100) = 100 + 20 = ₹120. Step 3: In year 2, price decreases by 10% of ₹120: Decrease = 10% of 120 = 12. New price = 120 - 12 = ₹108. Step 4: Net change = 108 - 100 = ₹8. Step 5: Net percentage change = (8/100) × 100 = 8%. Therefore, answer is B.

Question 3

The price of a commodity increases by 25% in the first year. In the second year, it decreases by 20% of the new price. In the third year, it increases by 10% of the price at the end of year 2. If the original price was ₹800, what is the percentage change in price from the original to the end of year 3?

Accepted Answer

Step 1: Original price = ₹800. After 25% increase in year 1: Price = 800 × 1.25 = ₹1000. Step 2: After 20% decrease in year 2: Price = 1000 × 0.80 = ₹800. Step 3: After 10% increase in year 3: Price = 800 × 1.10 = ₹880. Step 4: Net change = 880 − 800 = ₹80. Step 5: Percentage change = (80 ÷ 800) × 100 = 10%. Therefore, answer is C.

RRB Group D Percentage Change

Percentage Change— Rules & Concept

Key Points to Remember

Exam-Specific Tips

Percentage Change — Practice Questions

60-Second Revision — Percentage Change