During Children's Day on June 1st, the bookstore held promotional activities. All books in the children's bookstore are sold at a 30% discount. Xinhua Bookstore books "buy four get one free". In the sixth grade, I want to buy 20 interesting math books. Which bookstore is cheaper to buy?
Analysis: Students are very excited when they do problems independently. List the following four solutions:
The first type: the first step: first find the cost of going to the children's bookstore with less money.
20× (1-70%) = 6 (Ben)
Step 2: Ask Xinhua Bookstore for less money.
20(4+ 1)= 4 (Ben)
Step 3: Compare dimensions.
6>4
A: It's cheaper to buy it in a children's bookstore.
The second type: the first step: first find out the actual cost of the children's bookstore.
20× 70% = 14 (Ben)
Step 2: Find the actual cost of Xinhua Bookstore again.
20÷ (4+ 1) × 4 = 16 (Ben)
Step 3: Compare dimensions.
14< 16
A: It's cheaper to buy it in a children's bookstore.
The third type: using the hypothesis method.
Step 1: Suppose "Interesting Mathematics" is 1 yuan each.
Step 2: Find out the amount of money used less in the children's bookstore.
1× 20× (1-70%) = 6 (yuan)
Step 3: Find out how much money you spend in Xinhua Bookstore.
1× 20 ÷ (4+ 1) = 4 (yuan)
Step 3: Compare dimensions.
6>4
A: It's cheaper to buy it in a children's bookstore.
The fourth method: using the hypothesis method.
Step 1: Suppose "Interesting Mathematics" is 1 yuan each.
Step 2: Find out the amount of money used in the children's bookstore.
1×20×70%= 14 (yuan)
Step 3: Find out the amount of money to Xinhua Bookstore.
1× 20 ÷ (4+1) × 4 =16 (yuan)
Step 3: Compare dimensions.
14< 16
A: It's cheaper to buy it in a children's bookstore.