Aptitude Day 304

Problems on Chain rule: 

1. In a dairy farm, 20 cows eat 20 bags of husk in 20 days. In how many days one cow will eat one bag of husk?

 Solution:

                  Number of cows = 1: 20                                                            (Indirect proportion)

                                                                   :: Number of days = 20: x

                  Number of bags = 20: 1                                                             (Direct proportion)

                  1*20*x = 20*1*20

                  x = 20 days.

2. 3 men, working 3 hours a day can complete a work in 5 days. How many hours a day must 5 men work to complete the same work in 9 days?

Solution:

                  Number of men = 5: 3                                                            (Indirect proportion)

                                                                  :: Number of hours = 3: x

                  Number of days = 9: 5                                                            (Indirect proportion)

                  5*9*x = 3*5*3

                  x = 1 hour.