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Useful mathematical problems
1. Profit = (cost) × profit rate

2. The river ponds contracted by farmers harvested 23,000 Jin of hairy crabs this year, an increase of 15% over last year. So, last year, we harvested () kilograms of hairy crabs.

23,000 ÷ (1+15%) = 20,000 (kg)

3. If a commodity is sold in 95 yuan, it will lose 5%. If it is to make a profit of 15%, the selling price will be set at () yuan.

The cost is

95 ÷ (1-5%) = 100 (yuan)

The selling price is

100× (1+15%) =115 (yuan)

The price of a commodity rises by 25% first. If you want to restore the original price, you must reduce the price by ()%.

1- 1÷( 1+25%)=20%

5. If the grain output of a place this year is 12%, the grain output (b)

a . 1.2% b . 12% c . 88% d . 8.8%

6. This shop sells a pair of sports shoes at the cost of 80 yuan. The store sells it at a 20% discount, and there is a 40% profit margin. What's the price of each pair of sports shoes in this shop? If there is no discount, what is the profit margin?

The selling price is

80× (1+40%) =112 (yuan)

Pricing is

112÷ 80% =140 yuan

If there is no discount, the profit rate is

( 140-80)÷80=75%