2 x 99 = 198.
99 is 1 less than 100. Or we can say the difference between 99 and 100 is 1. If we double 99 (198) and double 100 (200) we are also doubling the difference between 99 and 100 (2x1 = 2). So we know that 2x99 is 2 less than 2x100. 200 - 2 = 198.
99 is 1 less than 100. Or we can say the difference between 99 and 100 is 1. If we double 99 (198) and double 100 (200) we are also doubling the difference between 99 and 100 (2x1 = 2). So we know that 2x99 is 2 less than 2x100. 200 - 2 = 198.