The sum of the three numbers in A.P is 21 and the product of the first and third number of the sequence is 45. What are the three numbers?

Answer: Option D

Let the numbers are be a - d, a, a + d
Then a - d + a + a + d = 21
3a = 21
a = 7
and (a - d)(a + d) = 45
a² - d² = 45
d² = 4
d = $$\pm$$ 2
Hence, the numbers are 5, 7 and 9 when d = 2 and 9, 7 and 5 when d = -2. In both the cases numbers are the same.