Helen and Sergey must cut down a row of trees. Helen can cut down the

Question

Helen and Sergey must cut down a row of trees. Helen can cut down the entire row in 3 hours, and Sergey can cut down the entire row in 7 hours. If they simultaneously start cutting trees, each starting at one end of the row and working towards each other, what fraction of the trees will Sergey have cut at the time they meet?

A. 1/10
B. 3/10
C. 3/7
D. 4/7
E. 7/10

A. 1/10
B. 3/10
C. 3/7
D. 4/7
E. 7/10

Archit3110 · Answer

Rate of Helen 1/3 trees per hr and Sergey 1/7 trees per hour
Together rate 10/21 
Serger have cut= 21/10*1/7= 3/10 trees IMO B

czar800 · Answer

ques has asked fraction
rates 1/3:1/7.
total work done by each one of them would be inverse of rates 7X:3X
fraction of sergey=3x/(3x+7x)=3/10. option B

ScottTargetTestPrep · Answer

Solution:

We can assume there are 21 trees. So Helen’s rate is 21/3 = 7 trees per hour and Sergey’s rate is 21/7 = 3 trees per hour. We can create the equation where x is the number of hours it takes to cut down all 21 trees when they work together:

7x + 3x = 21

10x = 21

x = 2.1

In 2.1 hours Sergey cuts 3 * 2.1 = 6.3 trees, which is 6.3/21 = 63/210 = 3/10 of the trees.

Alternate Solution:

In one hour, Helen can cut 1/3 of all the trees, and Sergey can cut 1/7 of all the trees. Together, they cut 1/3 + 1/7 = 10/21 of the trees in one hour. Thus, it will take the two 21/10 hours to cut down all the trees. Since Sergey can cut 1/7 of the trees in one hour, he will cut 21/10 * 1/7 = 3/10 of the trees in 21/10 hours.

Answer: B

PriyanshuR · Answer

Rate of Helen 1/3 trees per hr and Sergey 1/7 trees per hour
Together rate 10/21
Serger have cut= 21/10*1/7= 3/10 trees
 OPTION B

Jaival · Answer

The rates come out is the fraction of H:S AS 7:3. So sergey will have cut 3units by the time Helen finishes 7

Helen and Sergey must cut down a row of trees. Helen can cut down the

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Helen and Sergey must cut down a row of trees. Helen can cut down the

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