Aptitude Day 162

Problems on Average:

1. The average of 8 numbers is x and the average of 4 of these is y. If the average of the remaining is  z, then:

Solution:

                 x = (4y+4z)/ 8

                 x = 1/2(y+z)

                 2x = y+z.  

2. Out of 10 persons, 9 persons spent 20 each for their meals. The 10^th one spent 10 more than the average expenditure of all the 10. The total money spent by all of them was:

Solution:

                 Let the average be x.

                 x = [(9*20) + (x+10)] / 10

                10x = 180+x+10

                 x =21.11.

                 Total money spent = 10x = 211.10.