Question

Bob takes 8 hours to complete a job and Ben takes 10 hours to complete the same Job. How long will it take if Bob and Ben
work together but independenily to complete the same job?
1.40/9 days
2.90/4 days
3.419 days
4.33 4 days
​

Answer 1

Answer:

1. 40/9. hours.

Step-by-step explanation:

a hand written solution is attached

Answer 2

Concept:

To determine the value of a single unit from a specified multiple, use the unitary method. How to determine the value of one pen, for instance, if the cost of 40 pens is Rs. 400. The unitary approach can be used to complete it. Additionally, after determining the value of a single unit, we can multiply that value by the number of units needed to determine the value of the additional units. The concept of ratio and proportion is mostly applied using this way.

Given:

Bob takes 8 hours to complete a job and Ben takes 10 hours to complete the same Job.

Find:

How long will it take if Bob and Ben work together but independenily to complete the same job?

Solution:

Bob's 1 hour work =1/8

Ben's 1 hour work =1/10

Bob and Ben work together, 1 hour work =1/8+1/10

                                              =(5+4)/40

                                               =9/40

So, total work will be done is 40/9 hours

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