How long would it take person B to mow the lawn by himself?

Question

Twin brothers, person A and person B can mow their grandparents lawn together in 20 minutes. Person A could mow the lawn by himself in 9 minutes less time than it would take Person B. How long would it take person B to mow the lawn by himself?

Answer 1

Hi Amanda, 

We can solve by doing the following:

Let B=time it takes for B to mow the lawn Create Let Statements

B-9=time it takes for A to mow the lawn

Since we were given A+B=20 Write the given equation

we can substitute these let statements into the equation:

 

B+B-9=20 Substitute

2B=20+9 Solve for B

2B=29

B=29/2

B=14.5 minutes

∴It takes B 14.5 minutes to mow the lawn by himself.

We can also check our answer by plugging these values back into our original equation:

A+B=20

(14.5-9)+14.5=20

5.5+14.5=20

20=20

So, our answer was Correct! 

Best,

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