Concept:Form linear equations from the given age relationships and solve them to find the required ratio.
Explanation:Let Allen's present age be
A years and his son's present age be
S years.
Six years ago, Allen's age was
A−6 and his son's age was
S−6.
Given:
A−6=9(S−6).
Simplify:
A−6=9S−54, so
A=9S−48. ... (1)
Four years ago, Allen's age was
A−4 and his son's age was
S−4.
Given:
A−4=631​(S−4)=319​(S−4). ... (2)
Substitute
A=9S−48 into equation (2):
(9S−48)−4=319​(S−4)9S−52=319​(S−4)Multiply through by 3:
27S−156=19S−76So,
27S−19S=156−76, giving
8S=80.
Thus,
S=10 years.
Using equation (1):
A=9(10)−48=90−48=42 years.
After 6 years, Allen's age
=42+6=48 years.
After 6 years, son's age
=10+6=16 years.
Required ratio
=1648​=3 times.
Answer:Allen's age would be 3 times his son's age after 6 years, which matches option C.