(1) A factory produces a batch of small agricultural machinery. It is planned to produce 250 sets per month and complete them in six months. In fact, 50 sets are produced more than planned every month. How many months can the task be completed?

Solution: Assuming that it takes X days to complete the task, the proportional formula is (250+50)X=250×6.

(2) A pile of coal is used to burn 2.5 tons every day. After improving the method, it actually burns 2 tons every day. How many days can it burn in 30 days?

30×2.5=75 (ton) 75÷2≈38 (days) 38-30=8 (days)

A: Now you can burn for another 8 days.

③ The school-run factory assembles a batch of small household appliances. Plan 12 people to work 18 days. 3 days later, due to the urgent need of the production unit, it is required to be completed 5 days in advance. How many workers should be added?

12× 18=2 16

12×( 18-3)= 180

180÷ 12= 15 (days)

15-5= 10 (days)

18010 =18 (person)

18- 12=6 (person)

A: Six workers should be added.