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One person can do a certain job in twenty-one minutes, and another person can do the same job in twenty-eight minutes. How many minutes will it take them to do the job together?

6 min
12 min
24 min

User Mahek
by
9.2k points

2 Answers

2 votes

the correct answer is 12

User Munib
by
8.0k points
6 votes

Answer: 12 min

Explanation:

Given: Time taken by one person to do a job = 21 minutes

Time taken by another person to do a the same job = 28 minutes

If they work together then the total time taken by both of them to complete the job is given by :-


(1)/(T)=(1)/(21)+(1)/(28)\\\\\Rightarrow(1)/(T)=(4+3)/(84)\\\\\Rightarrow(1)/(T)=(7)/(84)\\\\\Rightarrow(1)/(T)=(1)/(12)\\\\\Rightarrow T=12

Hence, they will take 12 minutes to do the job together.

User Ditn
by
8.1k points

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