Concept:Raghu's age satisfies two nearby perfect-power conditions; find the age gap to the next perfect cube.
Explanation:Let Raghu's current age be
x years.
Last year his age was
x−1, which is a perfect square.
Next year his age will be
x+1, which is a perfect cube.
So the cube and the square differ by
2:
(x+1)−(x−1)=2.
The only nearby perfect powers fitting this are
25=52 and
27=33.
Thus,
x−1=25 and
x+1=27.
Hence, Raghu's current age is
x=26 years.
After 27, the next perfect cube is
64=43.
So he must wait from age 26 to age 64.
Required waiting time
=64−26=38 years.
Answer:Raghu must wait 38 years. Option C.