The time it takes to erect a bonfire is inversely proportional to the

Question

The time it takes to erect a bonfire is inversely proportional to the number of students doing the work. If it takes 20 students 1.5 hours to do the job, how long will it take 35 students to do the job, to the nearest minute?

(A) 51
(B) 52
(C) 53
(D) 54
(E) 55

(A) 51
(B) 52
(C) 53
(D) 54
(E) 55

D3N0 · Answer

Ans: B
from given relation t = time, n= number of students
t1n1=t2n2
so 20*3/2 = 35*t 
t= 6/7hrs means= 51.4 minuts approx so 52 minuts.
Ans: B

DavidTutorexamPAL · Answer

As we're told precisely what calculation to do, we'll just do it.
This is a Precise approach.

Since 20:35 = 4:7, that is we need to increase 20 by a factor of 7/4 to get to 35, then we need to decrease 1.5 hours by a factor of 7/4 to get our answer.
(we'll write 90 minutes instead of 1.5 hours as this is easier)
90 / (7/4) = 90 * 4 / 7 = 360 / 7 = (350 + 7 + 3)/7 = 50 + 1 + 3/7 = 51 3/7.
The nearest minute, that is the closest minute larger than 51 3/7 is 52.

(B) is our answer.

pushpitkc · Answer

Given:   Time(let us call it t) is inversely proportional to the number of students who work(let that be n)

t = \frac{k}{n}  where k is the constant

To find the value of the constant ->  90 = \frac{k}{20}  ->  k = 1800

If there are 35 students, the time taken can be calculated as follows: t =  \frac{1800}{35} = \frac{360}{7} = 51.42 minutes (Option A)

dkumar2012  - 51.42 is closer to 51 than 52. Please make the necessary change

D3N0 · Answer

pushpitkc  :
Question asks for the completion time. so anything greater than 51 minutes will be consider as 52 minutes to complete.

EgmatQuantExpert · Answer

Solution

Given:  
 • The time taken to erect a bonfire is inversely proportional to the number of students doing the work
• 20 students take 1.5 hours to do the job

To find:  
 • The time 35 students will take to do the job, to the nearest minute

Approach and Working:   
If 20 students take 1.5 hours to do the job, 
 • The total job in terms of man-hours = 20 * 1.5 = 30

If 35 students do the same job, 
 • The time taken =  \frac{30}{35}  hours =  \frac{30}{35} * 60  minutes = 51.4 minutes

As per the question statement, the nearest minute to complete the job should be 51 minutes, although to complete the job it would take more than 51 minutes and less than 52 minutes

Hence, the correct answer is option A.

Answer: A

D3N0 · Answer

Here the question states: "how long will it take 35 students to do the job, to the nearest minute?" Nearest minute to 51 is 50.5-51.49 in this case for the whole set work is not done yet. but for the nearest 52 minutes 51.5-52.49 work is done..

Are we thinking about how long will it take to complete the job and then asking : ok now what is the nearest Minute to it???

SajjitaKundu · Answer

I think the nearest minute should be 51 as we are rounding off to the nearest integer, so the answer should be A.

US09 · Answer

IMO nearest minute should be 51. Looking forward to the OE.

MathRevolution · Answer

20 students take 1.5 hours or 90 minutes to do the job

Time taken is inversely proportional to No. of students.

Hence, 1 student will take more time and therefore 20*90 = 30 hours or 1800 minutes.

35 students will take less time and therefore :  \frac{30 }{ 35}  hours or  \frac{30 }{ 35}  * 60 minutes = 51.42.

To the nearest integer, it will be 51 minutes.

Answer A

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The time it takes to erect a bonfire is inversely proportional to the

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