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.

Why this formula given below does not work with this question but works with other such similar questions?

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

We found a new method.
step 1- calc the total time for 3 pumps ie(2*8)
2- now for 1 pump time=(2*8)*3
3- " " 4 pump time = ((2*8)*3)/4..ans.

(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.

pumps*days*hours=pumps*days*hours.

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

x=12.

That's simple

As tank are Same.

So 3x8=24 hours required for 1 day for that tank.

So hrs will be same.

For 4 tanks, 4x6=24 for 2 days.

If it 1 day, 6x2=12 hours.

Can anyone just explain the chain rule with direct and indirect proportion?

3 pumps -> 8h -> 2 days.

4 pumps -> ? -> 1 day.

3*8*2/4*1 = 12.

One pump requires 16 *3 = 48 hrs to empty the tank.

4 pump requires 48/4 = 12 hrs.

At First we find the Total_hour to finish the work, that is:

3*8*2 = 48.

So, 4*X*1 = 48.

X = 48/4 = 12.