Aptitude - Chain Rule - Discussion

The equation is 30 x 6 x x = 39 x 5 x 12 not clear to understand.

Please explain it clearly. When I solved this problem I got equation as 39 x 12 x 5 = 30 x x x 6.

How come you got that equation?

Ya. Right. Even I got so!

Why not we say 39 persons did work in (12*5) hours.

Then what would be 30 persons working for (x*6) hours ?

I always solve this as a work and time problem:
39 people working 5 hours a day finished 1/12th the work in 1 day.
39 people will therefore finish 1/60th (1/12 x 1/5) the work in 1 hour.
1 person will finish (1/60 x 1/39)th the work in 1 hour
So 30 people working for 6 hours will finish:
(1/60) x (1/39) x 6 x 30 = everything cancels out and you are left with 1/13th.
So: 30 people working for 6 hours will finish 1/13th the work in a day meaning they will take 13 days to finish.

Ny cross multiplication method i didn't get correct ans.....
39---->12*5hrs
then 30---->x*6hrs

Now 30*12*5=39*x*6
then 30*12*5/39*6=x......... then i got 100/13........
is it correct or wrong

Hope you all understand....

First codition=total hours to complete the work=39 persons * 12 days * 5 hr

Second codition=total hours to complete the work=30 persons * x days * 6 hr

since the work is still the same so
39*12*5=30*x*6
x=13

I thing the easy way to solve this out is below.

39 12 5

30 x 6

after cross multiplication, we will have

39 1

3 x

According to rule
39x = 3
x = 3 / 39

now due to indirect relation we will change the above equation as::: x = 39/3 which results ===13

Thanks

There is simple formula for this type of questions:

M1D1H1 M2D2H2
------ = ------
W1 W2

Where,

M = No.of Men
D = No.of Days
H = No.of Hours
W = Amt of Work done.

In this problem, if we apply this equation,

39*12*5 = 30*6*x

x=13 is the answer.

I have a question plz answer:

12 men or 15 women completes a piece of work in 66 days, 24 men and 3 women together can complete in in how many days?

@subhi.

12 men completes a piece of work in 66 days.
=> Work done by 12men/day = (1/66)th part.
=> Work done by 1man/day = (1/66*12)= (1/792)th part.

Similarly,
15 women completes the work in 66 days.
=> Work done by 15women/day = (1/66)th part.
=> Work done by 1women/day = (1/66*15)= (1/990)th part.

Now.. 24men and 3women together.
So, calculate work done by (24men and 3women)/day.
=> (24/792)+(3/990)
=> (1/33)+(1/330)
=> (11/330) = 1/30.

=> Work done by (24men and 3women)/day= (1/30)th part.
=> Total no.of days to complete the work is 30 days.

M1D1H1 M2D2H2
------ = ------
W1 W2

Where,

M = No.of Men
D = No.of Days
H = No.of Hours
W = Amt of Work done.

In this problem, if we apply this equation,

39*12*5 = 30*6*x

x=13 is the answer.