I'm going to use the formula Romonosov, a famous Russian mathematician, borrowed a book "principles of mathematics" from his neighbor. The neighbor said to him, "help me chop firewood for 10 days. I'll give you the book and give you another 20 rubles. " As a result, he only cut firewood for seven days. After the neighbor gave him the book, he paid five rubles. What is the price of the book "principles of mathematics"?

I'm going to use the formula Romonosov, a famous Russian mathematician, borrowed a book "principles of mathematics" from his neighbor. The neighbor said to him, "help me chop firewood for 10 days. I'll give you the book and give you another 20 rubles. " As a result, he only cut firewood for seven days. After the neighbor gave him the book, he paid five rubles. What is the price of the book "principles of mathematics"?

Step 1: the number of days to cut less; 10-7 = 3 (days)
Step 2: the number of rubles less; 20-5 = 15 (rubles)
Step 3: daily payment; 15 △ 3 = 5 (rubles)
Step 4: the total reward for 7 days; 5 × 7 = 35 (rubles)
Step 5: book price. 35-5 = 30 rubles
Comprehensive formula: (20-5) / (10-7) × 7-5

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Romonosov, a famous Russian mathematician, borrowed a book "principles of mathematics" from his neighbor. The neighbor said to him, "if you help me chop firewood for 10 days, I will give you the book and another 20 rubles." as a result, he only chopped firewood for 7 days. After the neighbor gave the book to him, he paid another 5 rubles. What is the price of the book?

30 rubles
10-7＝3
20－5＝15
15÷3＝5
20÷4＝4
10-4＝6
5*6＝30

New time and space for winter vacation in grade five

Page 2:
1: Fear specific distance resistance
Stern and handsome
2: If nothing happens, there will be nothing left. Knowing people and being good at their duties, they will be trapped at home and abroad. The world is dark and the world is dark. Now they are not willing to sacrifice themselves for others
3: We should study more for a day. If there is no book, Pepsi will be desolate