Question 1102223
The multiples of 5 between 1 and 200 are 5, 10, 15, ..., 200
This forms an arithmetic sequence with first term equal to 5 and common difference equal to 5.
The nth term is written a_n = 5 + (n-1)*5 = 5n
The sum of the 1st n terms of an arithmetic sequence is S_n = (n/2)(a + a_n),
where a = the 1st term
The last term is 200, so n = 200/5 = 40
S_40 = 20*(5 + 200) = 4100