By how much should the number 640 be reduced to get the product of the number 60 and 9.

In order to solve this problem, you will need some knowledge in the field of multiplication and subtraction.

1) First, let’s multiply 60 by 9 in order to find out what number in the end we need to get:

60 * 9 = 540;

2) Then you need to subtract the number 540 from 640:

640 – 540 = 100;

The number 100 is the number by which 640 must be reduced in order to end up with the product of 60 by 9;

The answer is 100;