Aptitude - Chain Rule - Discussion

Let pumps - 'p', no.of hrs/day - 'h', no.of days - 'd'.

For this type of problems, first know what we have to find? here we have to find hrs/day i.e. 'h'.

Now, find out the relation of 'h' with other parameters 'p' and 'd'.

If no.of pumps increases, no.of hrs/day decreases (inverse proportion).

p & (1/h). (1) **Assume &-proportionality symbol**.

If no.of days increases, no.of hrs/day decreases (inverse proportion).

d & (1/h). (2).

From (1) & (2).

pd & (1/h). (3).

=> pdh=constant.

=> p1*d1*h1=p2*d2*h2.

=> 3*2*8=4*1*x.

=> x=12.

If 38 men, working 6 hours a day, can do a piece of work in 12 days, find the number of days in which 57 men working 8 hours a day, can do twice that piece of work, supposing that two men of the first set do as much work in 1 hour as 3 men of the second set do in 3/2 hours whats the answer for this?

Can Anyone answer for this?

3 pumps 8 hours 2 days =work
3*8*2=work----->eqn1

now to complete the same work with 4 pumps in 1 day how many hours are required? lets take the hours required as x. then we can write the same work as

4 pump x hours 1 day =work

4*x*1=work ---->eqn2

equating both equation
3*8*2=4*x*1
x=48/4
x=12 hours

@Cauverypithan
Math master is rite....coz 3 pumps will empty in 16hrs....
if they r using one pump,then work load ll increase,then 48hrs is rite....
still not clear...
then c...3 pump ll empty one tank in 16hr...so more the no of pump faster it gets emptied,
lesser the no of pump slower it gets emptied...

Please solve my problem

If 38 men , working 6 hours a day ,can do a piece of work in 12 days , find the number of days in which 57 men working 8 hours a day, can do twice that piece of work, supposing that two men of the first set do as much work in 1 hour as 3 men of the secand set do in 3/2 hours.

3 pumps = 8 hrs/day.

1 pump = 8*3 = 24 hrs/day and 48 hrs in 2 days.

Considering 1 day work of 3 pumps we know that 24/3 = 8.

Now f we consider 1 day work of 4 pumps should not it be 24/4 = 6.

Please anyone, why? are we considering for two days when it is asked for 1 day work?

There is simple and understandable style to solve:

3 pumps take 24 hrs total (8 Hrs a day).

If 1 pump will be working then, it will need 8*3 = 24 hrs.

1 pump need 24 Hrs in two day.

1 pump need 24*2 Hrs in one day.

If I contribute 4 pumps then.

48/4 = 12 hrs.

Please solve my problem.

1200 men 500 women can build a bridge in 2 weeks. 900 men and 250 women will take 3 weeks to build the same bridge. How many men will be needed to build the bridge in one week?

(Machine (1) x Time) /Work = (Machine (2) x Time) /Work.

This formula works here also
3 * 8(hrs)* 2(day) /1 =4 * x(hrs) * 1(day)/1
==> x= 12

Here work done is 1 since full tank is to be emptied.

@math master and all.

Your approach is right because fortunately question is asking of 1 day. If not. Then we have to divide the answer by number of days. So people take care of that also.