Percentage increase or decrease

The idea

Percentage increase (or decrease) = (amount of increase or decrease) ÷ (original amount or base) × 100.

How much did tomatoes rise?

Three years ago, 1 kg of tomatoes cost ₹30. Now it costs ₹42. The price went up by ₹12.

By what percentage did the price increase?

• 12%
• 29%
• 40%

Before and now

The top bar is the original amount. The bottom bar is the amount now. Move the new value and watch the change and its percentage. Two situations are in the tabs.

Change compared with the original

Percentage increase (or decrease) = (amount of increase or decrease) ÷ (original amount or base) × 100.

Tomatoes: the price rose from ₹30 to ₹42, an increase of ₹12. 12/30 × 100 = 40% The price increased by 40%.

Theatre: the footfall fell from 160 to 100, a decrease of 60. 60/160 × 100 = 37.5% The footfall decreased by 37.5%.

Always divide by the original amount (the base), the amount you started from, not by the new amount.

Notes

Percentage increase (or decrease) = (amount of increase or decrease) ÷ (original amount or base) × 100.

Check yourself

A bus ticket rose from ₹20 to ₹25. What is the percentage increase?

Answer: 25 %

The increase is 25 − 20 = 5. 5/20 × 100 = 25%

A class had 250 students present on Monday and 200 on Tuesday. What is the percentage decrease?

Answer: 20 %

The decrease is 250 − 200 = 50. 50/250 × 100 = 20%

The price of 1 kg of onions was ₹40. It increased by 15%. By how much did the price increase (in ₹)?

Answer: 6

The increase is 15% of the original price. 15/100 × 40 = 6, so ₹6.

A price went from ₹50 to ₹40. What is the percentage decrease?

• 20% — correct. Yes! The decrease is 10, and the base is the original price, ₹50. 10/50 × 100 = 20%
• 25%. That divides by the new price (10 out of 40). Divide by the original price, ₹50, instead.
• 10%. That is the decrease in rupees. The percentage is 10 out of the original 50, which is 20%.