Aptitude - Chain Rule

Let the required number of working hours per day be x.

More pumps, Less working hours per day (Indirect Proportion)

Less days, More working hours per day (Indirect Proportion)

Pumps	4	:	3		:: 8 : x
Days	1	:	2

4 x 1 x x = 3 x 2 x 8

x =	(3 x 2 x 8)
	(4)

x = 12.

Cost of x metres = Rs. d.

Cost of 1 metre = Rs.		d
		x

Cost of y metres = Rs.		d	. y		= Rs.		yd	.
		x					x

Let the required number of bottles be x.

More machines, More bottles (Direct Proportion)

More minutes, More bottles (Direct Proportion)

Machines	6	:	10		:: 270 : x
Time (in minutes)	1	:	4

6 x 1 x x = 10 x 4 x 270

x =	(10 x 4 x 270)
	(6)

x = 1800.

After 10 days : 150 men had food for 35 days.

Suppose 125 men had food for x days.

Now, Less men, More days (Indirect Proportion)

125 : 150 :: 35 : x       125 x x = 150 x 35

x =	150 x 35
	125

x = 42.

Let the required number of days be x.

Less persons, More days (Indirect Proportion)

More working hours per day, Less days (Indirect Proportion)

Persons	30	:	39		:: 12 : x
Working hours/day	6	:	5

30 x 6 x x = 39 x 5 x 12

x =	(39 x 5 x 12)
	(30 x 6)

x = 13.