The average age of fifteen persons is 32 years. If two more persons are added then the average is increased by 3 years. The new persons have an age difference of 9 years between them. The age (in years) of the younger among the new persons is:
Given the average age of fifteen persons is 32 years.
Let the 15 persons be $$\ a_{1}, a_{2}, a_{3}, a_{4}.........a_{15} $$
=> $$ \frac {a_{1}+ a_{2}+a_{3}+a_{4}+.........+a_{15} } {15}$$Â = 32
=> $$\ a_{1}+a_{2}+a_{3}+a_{4}+.........+a_{15} = 15 \times 32 $$Â
=> $$\ a_{1}+a_{2}+a_{3}+a_{4}+.........+a_{15} = 480 $$.......(1)
If two more persons are added then the average is increased by 3 years.
Let those persons be $$\ a_{16}, a_{17} $$ respectively
$$ \frac {a_{1}+ a_{2}+a_{3}+a_{4}+.........+a_{15}+a_{16}+a_{17} } {17}$$Â = 35
=> $$ \ {a_{1}+ a_{2}+a_{3}+a_{4}+.........+a_{15}+a_{16}+a_{17} } = 35 \times 17 $$
=> $$ \ {a_{1}+ a_{2}+a_{3}+a_{4}+.........+a_{15}+a_{16}+a_{17} }$$ = 595 ......(2)
Substituting (1) in (2) we will get
480 + $$ \ a_{16}+a_{17} $$ = 595
 => $$ \ a_{16}+a_{17} $$ = 595 - 480
=> $$ \ a_{16}+a_{17} $$ = 115 ......(3)
Also given, the new persons have an age difference of 9 years between them
=> $$ \ a_{16} - a_{17} $$ = 9 .......(4)
Solving (3) and (4) we get,
$$\ 2a_{16} $$ = 115+9
=> $$\ 2a_{16} $$ = 124
=> $$\ a_{16} $$ = 62
Hence $$\ a_{17} $$ = 115 -62 = 53
Create a FREE account and get: