Question

Connie can wash nine windows in one hour. Rick can wash seven windows in one hour. Connie has been washing windows for one hour, when Rick joins her to finish the job. The entire job consists of washing 57 windows. How many hours does Rick work?

Answer 1

Answer: Rick worked for three hours with Connie and washed 21 windows.

Given : Connie washes nine windows in one hour. While Rick washes seven windows in one hour.  

To find : how many hours Rick worked.

Explanation:

As we know, Connie started the work one hour before Rick joined. In that one hour he finished washing nine windows as per his efficiency. Then after an hour Rick joined and both washed sixteen windows together in an hour.

Mathematically,

Connie washed in an hour $= 9 windows$,

Connie and Rick together in an hour $= 9+7 = 16$ windows.

In first hour windows cleaned $= 9$,

In second hour windows cleaned $= 9+7 = 16$,

Similarly, also in third and fourth hour windows cleaned $= 16+16$

Total work in four hours $= 9+16+16+16 = 57$

So, Rick worked in the second, third and fourth hour and washed $7$×$3 = 21$ windows .

Hence, we conclude that Rick worked for three hours and washed 21 windows.

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