We can solve this question in two ways. The first method is to divide 6.71 x 10 ^ 8 by 60 and get the speed for one minute and then multiply the remaining answer by 90 to get for 90 complete minutes.
But what i will do is that i will divide it by 2 which will give us the time for 30 minutes and then multiply it by 3 so we get the answer for 90 minutes. So the answer is 4.26x 10^ 8 multiplied by 3.