Question

mark can cleaN the house in 7 hours. when he cleans the same house with wend, it takes them 3 hours to clean the house. how long would it rake wendy to clean the house by herself

Answer 1

Answer:5.25

Step-by-step explanation:

3(1/7 + 1/x) = 1

3([x + 7]/7x) = 1

3x + 21 = 7x

4x = 21

x = 21/4 OR 5.25

Answer 2

It will take wendy 5.25hrs to clean the house by herself.

• Let x be the time taken by mark to clean the house by herself
• Let y be the time taken by wend to clean the house by herself
• Let a be the time it took the two to clean the house together.

In order to get the time it take wendy to clean the house by herself, we will use the expression:

1/a = 1/x + 1/y

1/3 = 1/7 + 1/y

1/y = 1/3 - 1/7

1/y = 7-3/21

1/y = 4/21

y =  21/4

y =  5.25hrs

Hence it will take wendy 5.25hrs to clean the house by herself.

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