Number System
The sum of the ages of a son and father is 65 years. After 5 years the age of father will be double of the age of son. What is the age of son ?
Let the age of the son be x and the age of the father be y.Therefore, x + y = 65 ..........(i)or, 2 x (x + 5) = (y + 5)or, 2x + 10 = y + 5or, 2x - y = 5 ...................(ii)From equations (i) and (ii), x = 20, y = 45
A total of (7 + 3) persons = 10 personal can sit in 10! ways.If we consider three girls as one unit, total persons = 7 + = 8 (here all three girls sit together).No. of ways = 81 and the three girls can be arranged in 31 ways among themselves.So, the total number of ways when three girls sit together = 81 x 31When the girls don't sit together, number of ways = 101 - (81 x 31) = 81 (10 x 9 - 6) = 81 x 84 = 3386880
EXAMIANS