If you round 62 down to 60 and 22 down to 20, it is easy to multiply them together in your head. Just multiply 6 and 2 and add two 0s.
Knowing that 60 × 20 = 1200, we can tell that the product of 62 × 22 has to be larger, since we rounded down to get 1200.
1042 < 1200, so we know the answer is not reasonable.
