analyse

120÷ 20%=600 (Ben)

180÷600=30%

600×50%=300 (Ben)

So the answer is: 600 books; 30%; 300 copies

Mathematical percentage application problem answer:

1. The output value of a chemical fertilizer plant increased by 20% this year, reaching 5 million yuan. What is the output value this year?

Analysis: The output value of a chemical fertilizer plant increased by 20% and 5 million yuan compared with last year. Last year's output value was 500 ÷ 20% = 2,500 (ten thousand yuan), and this year's output value is 2,500+500 = 3,000 (ten thousand yuan).

Solution: 500÷20%=2500 (ten thousand yuan), 2500+500=3000 (ten thousand yuan).

A: This year's value is 30 million yuan.

2. The fruit company stores a batch of apples, and delivers them after selling 30% 160 boxes, which is more than the original apples110. How many boxes of apples are there?

Analysis: Assuming that the original apple is X, this batch of apples will be shipped 160 boxes after being sold for 30%, which is more than the original apple110, x × (1-30%)+160 = (65430)

Solution: Set the original Apple X box, as can be seen from the meaning of the problem:

X× (1-30%)+160 = (1+110) x, when solving the equation, X=400.

Apples are more than the original storage110, (1+1/kloc-0) × 400 = 440 (box).

There are 440 boxes of apples.

3, a commodity, the original price is 20% less than the current price, the current price 1028 yuan, what is the original price?

Analysis: The original price is 20% cheaper than the current price. Current price 1, original price 1-20%, current price 1028 yuan, original price1028× (1-20%) = 822.4 yuan.

Solution:1028× (1-20%) =1028× 80% = 822.4 (yuan)

A: The original price is 822.4 yuan.