time per math problem = 4.5 x 10 ^-5
number of math problems= 3 x 10^6
Multiply both expressions:
4.5 x 10^-5 x 3x 10 ^6
(4.5 x 3 ) ( 10^[-5+6] )
13.5 x 10^1 = 135
135 seconds
1.6m questions
2.0m answers