Two years ago, a man's age was three times the square of his son's age.In three years time, his age will be four times his son's age.Find their present age.

Asked by singhaivk05 | 6th Mar, 2015, 11:04: PM

Expert Answer:

L e t space t h e space p r e s e n t space a g e space o f space t h e space m a n space a n d space h i s space s o n space b e apostrophe m apostrophe space y e a r s space a n d space apostrophe s apostrophe space y e a r s space r e s p e c t i v e l y. T w o space y e a r s space a g o comma M a n apostrophe s space a g e space equals space left parenthesis m minus 2 right parenthesis S o n apostrophe s space a g e space equals space left parenthesis s minus 2 right parenthesis left parenthesis m minus 2 right parenthesis equals 3 left parenthesis s minus 2 right parenthesis squared m minus 2 equals 3 s squared minus 12 s plus 12 m equals 3 s squared minus 12 s plus 14...... left parenthesis i right parenthesis  T h r e e space y e a r s space l a t e r comma M a n apostrophe s space a g e space equals space left parenthesis m plus 3 right parenthesis S o n apostrophe s space a g e space equals left parenthesis s plus 3 right parenthesis m plus 3 equals 4 left parenthesis s plus 3 right parenthesis m minus 4 s equals 9......... left parenthesis i i right parenthesis  E q u a t i n g space left parenthesis i right parenthesis space a n d space left parenthesis i i right parenthesis comma 4 s plus 9 equals 3 s squared minus 12 s plus 14 3 s squared minus 16 s plus 5 equals 0 3 s squared minus 15 s minus s plus 5 equals 0 3 s left parenthesis s minus 5 right parenthesis minus 1 left parenthesis s minus 5 right parenthesis equals 0 left parenthesis 3 s minus 1 right parenthesis left parenthesis s minus 5 right parenthesis equals 0 s equals 5 comma space s equals 1 third left square bracket N o t space p o s s i b l e right square bracket therefore s equals 5 space y e a r s m equals 29 P r e s e n t space a g e space o f space m a n space equals 29 space y e a r s P r e s e n t space a g e space o f space s o n space equals space 5 space y e a r s

Answered by Prasenjit Paul | 7th Mar, 2015, 11:08: AM