Answers

1. We have

   140 = 7·20

   and

   300 = 294 + 6 = 7·42 + 6

   This tells us that there are 42 – 20 + 1 = 23 multiples of 7 in the list. Notice that the first and last multiple are both even. The multiples occur in a pattern of {even, odd, even, odd, …, even} so that 12 (number of multiples plus 1, divided by 2) are even and 11 (23 – 12) are odd.

   So there are 11 multiples of 7 not divisible by 14 in the list.

   Reply