Q7 of 227 Page 107

One year ago, a man was 8 times as old as his son. Now his age is equal to the square of his son’s age. Find their present ages.

Let x be the present age of son


Let ‘y’ be the present age of father


So, x – 1 be the age of son one year age


y – 1 be the age of father one year ago.


By using the given information


y = x2


y – 1 = 8(x – 1)


⇒ y = 8x – 8 + 1


⇒ y = 8x – 7


⇒ x2 = 8x – 7


⇒ x2 – 8x + 7 = 0


⇒ x2 –x – 7x + 7 = 0


⇒ x(x – 1) –7(x – 1) = 0


⇒ (x – 1)(x – 7) = 0


X – 1 = 0 or x – 7 = 0


x = 1 or x = 7


Therefore, age of father is 49.


More from this chapter

All 227 →
5

A train covers a distance of 90 km at a uniform speed. Had the speed been 15 km/hr more, it would have taken 30 minutes less for the journey. Find the original speed of the train.

 6

The speed of a boat in still water is 15 km/hr. It goes 30 km upstream and return downstream to the original point in 4 hrs 30 minutes. Find the speed of the stream.

 8

A chess board contains 64 equal squares and the area of each square is 6.25 cm2. An order around the board is 2 cm wide. Find the length of the side of the chess board

 9

A takes 6 day less than the time taken by B to finish a piece of work. If both A and B together can finish it in 4 days, find the time that B would take to finish this work by himself.