Question

Find the sum of the integers between 1 to 201 which are multiple of 4.

Answer 1

for this we will use formulas of ap 
$a_{n}$ = a + (n-1)d
d = 4 (multiple of d)
n = ?
a = 1
$a_{n}$ = 201
therefore , 201=1+(n-1)4
201 = 1+4n-4
201 = 4n-3
204=4n
n = 51
so , there are 51 int b/w 1 and 201 
to find the sum we will use 
$s_{n}$ = n/2(l+a)
$s_{n}$ =?
n = 51 
l = 201
a = 1
$s_{51}$ = 25.5(201+1)
$s_{51}$ =5151
sum of the integers between 1 to 201 which are multiple of 4 is 5151