Question

9 students can make a poster in 10 hours. How many students should join them so that they altogether can make this poster in 6 hours?

Answer 1

6

Explanation:

The work involved in making the poster is the product of students and hours:

work = students × hours = (9 students)(10 hours) = 90 student·hours

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needed

If hours are reduced to 6, the necessary number of students is ...

90 student·hours = (6 hours)(students)

(90 student·hours)/(6 hours) = 15 students . . . . . . divide by 6 hours

additional

If 15 are needed, then the number that must be added is ...

15 -9 = 6 . . . . students need to be added