You should look for ways to simplify here before attempting to multiply.
sqrt(45) times sqrt(96) can be rewritten in terms of perfect squares and other factors:
45 = 5 * 9 (9 is a perfect square)
96 = 16 * 6 (16 is a perfect square)
Then sqrt45) times sqrt(96) = sqrt(9)*sqrt(5)*sqrt(6)*sqrt(16)
= 3 * sqrt(5) * sqrt(6) * 4
= 12sqrt(30) (answer)
30 can be factored, but none of the factors of 30 are perfect squares.