If 5 people, each working at a constant rate can wash 8 cars in 40 mins, How many people working at a same constant rate are needed to wash a cars in b hours?
A) $$\frac{a\ }{60b}$$
B)$$\frac{5a}{12b}$$
C)$$\frac{a}{12b}$$
D)$$\frac{a}{20b}$$
E) $$\frac{25a}{b}$$
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If 5 people, each working at a constant rate can wash 8 cars
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AbhishekRyu
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regor60
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Since you know that 5, 8 and 40 minutes = 40/60 hours works, use this information to test the answers by using a=8 and b =40/60 =2/3 hours to see if any of the answers delivers the known answer of 5AbhishekRyu wrote:If 5 people, each working at a constant rate can wash 8 cars in 40 mins, How many people working at a same constant rate are needed to wash a cars in b hours?
A) $$\frac{a\ }{60b}$$
B)$$\frac{5a}{12b}$$
C)$$\frac{a}{12b}$$
D)$$\frac{a}{20b}$$
E) $$\frac{25a}{b}$$
A. a/60b = 8/(60*(2/3)) = 8/40 = 1/5 > not equal to 5
B. 5a/12b = (5x8)/(12x(2/3)) = 40/8 = 5 > equals 5 correct answer
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Hi All,
We're told that 5 people, each working at a constant rate, can wash 8 cars in 40 MINUTES. We're asked how many people working at that same constant rate are needed to wash A cars in B HOURS. With these types of questions, it often helps to determine the total amount of work needed to complete a job.
Here, we have 5 people working for 40 minutes EACH. That's (5)(400) = 200 people-minutes of work needed to wash 8 cars.
By extension, it would take 200/8 = 25 people-minutes of work to wash 1 car.
Thus, to wash 1 car:
1 person would need 25 minutes
2 people would need 12.5 minutes each
3 people would need 8 1/3 minutes each
Etc.
We can use this work rate against the given question. Since 1 car wash requires 25 minutes of work, that's 25/60 = 5/12 hours for 1 person to wash 1 car. Thus, we're looking for an answer that equals 1 when A=1 and B=5/12. There's only one answer that matches....
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
We're told that 5 people, each working at a constant rate, can wash 8 cars in 40 MINUTES. We're asked how many people working at that same constant rate are needed to wash A cars in B HOURS. With these types of questions, it often helps to determine the total amount of work needed to complete a job.
Here, we have 5 people working for 40 minutes EACH. That's (5)(400) = 200 people-minutes of work needed to wash 8 cars.
By extension, it would take 200/8 = 25 people-minutes of work to wash 1 car.
Thus, to wash 1 car:
1 person would need 25 minutes
2 people would need 12.5 minutes each
3 people would need 8 1/3 minutes each
Etc.
We can use this work rate against the given question. Since 1 car wash requires 25 minutes of work, that's 25/60 = 5/12 hours for 1 person to wash 1 car. Thus, we're looking for an answer that equals 1 when A=1 and B=5/12. There's only one answer that matches....
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
