How many multiples of 5 are there between 199 and 1,198? hint: an = a1 + d(n − 1), where a1 is the first term and d is the common difference.

An=a1+d (n-1)
A1=200 since that's the first term that can be a multiple of 5
N=? That's what we need to find
An=1195 since that's the last multiple of 5 that we can use
D=5
Plug in
1195=200+5 (n-1)
-200 both sides
995=5 (n-1)
Distribute 5 to n-1
995=5n-5
+5 both sides
1000=5n
÷5 both sides
N=200 there are 200 multiples of 5 in between 199 and 1198