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3/6 Sandcastle

Two children can build a sandcastle in 3 hours. Susan can build three times as fast as Jane. How long will it take Jane to build the castle by herself?

Jane's rate + Susan's rate = 1/3

Susan's rate is three times that of Jane's rate. r+3r =1/3.

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Comments (3)

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Trustin mesays...

The rate is one castle in three hours: 1/3

Multiply ratio by 4 to make numerator divisible into 4 equal parts: 4/12

Susan can build 4 times as fast therefore, Susan's rate is 3/12, while Jane's rate is 1/12:

(3/12 + 1/12 = 4/12)

In 1 hr Jane can build 1/12th of a sandcastle, therefore she needs 12 hours to build a complete sandcastle by herself.

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massysays...

Rate for both children is 1 job in 3 hours (1/3)

Susan's rate is three times that of Jane's rate

Jane's rate + Susan's rate = 1/3

r+3r =1/3

r=1/12

It would take Jane 12 hours to build one sandcastle

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Charlie3says...

r+3r =1/3

r=1/12

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