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Higher Mathematics Problems in Primary Mathematics
1. It takes 15 days for mentoring to process a batch of parts. If the master does 10 days first, the apprentice will do the rest of the work alone 17 days. How many days will it take if the apprentice processes these parts alone?

A: The master can complete X pieces in one day, and the apprentice can complete Y pieces in one day. The total number of parts is S.

s =(x+y)* 15 = = & gt; y=s/ 15-x

s- 10y= 17x

s- 10 *(s/ 15-x)= 17x

s-2s/3+ 10x= 17x

s/3=7x

s=2 1x

Therefore, it takes 2 1 day for the apprentice to complete this batch of parts alone.

2. The senior students took 40% of the original story books in the school, and the administrator bought 180 books from the bookstore, just taking 25% of the books. How many books did the senior students take?

Answer: suppose there are x story books.

25%*(40%*x)= 180

1/4*2x/5= 180

2x/20= 180

x= 1800

The number of books brought by senior students is 1800*40%=720.

So, the seniors took 720 copies.

3. The store bought some soccer balls and sold them at 1 12% of the original price, with a unit price of 67.2 yuan each. When 50 footballs were sold, the full cost was recovered. How many footballs did the shop buy?

A: suppose there are x footballs, and the original unit price is S.

1 12%*s=67.2 s=60

60x=50*67.2

x=56

So, the store bought 56 footballs.

4, two engineering teams, one team has 120 people, 20% of the number of the first team is transferred to the second team, and two-thirds of the number of the second team is exactly three-quarters of the number of the first team. How many people are there in the second team?

A: let the original number of the second team be X.

(x+ 120 * 20%)* 2/3 =( 120- 120 * 20%)* 3/4

x=84

The number of people less than the first team is 120-84=36.

5. Group A and Group B work together on a project, and can complete 9/40 of the tasks every time. Team a worked alone for 3 days, team b worked alone for 5 days, and the remaining one-eighth of the tasks were not completed. If all the projects are completed by team B alone, how many days will it take?

A:

[1-1/8-3× (9/40)] ⊙ (5-3) =110 for team b to complete all projects every day.

Team B does it alone, and it takes1÷ (110) =10 days to complete it.