Question

find the sum of all even number between 1 and 350​

Answer 1

first term= 2 =a

last term 350 =l

common difference= 2

sum of all even numbers between 1 and 350=Sn =n/2(a+l)

number of terms = n

a+(n-1)d=350

(n-1)2=348

n-1=174

n=175

sum of all even numbers = Sn = 175/2(2+350)

=175/2(352)

=175(176)

=30800

Answer 2

Formulaes used are :-

$t \frac{}{n} = a \: + \: ( \: n \: - \: 1 \: ) \: d \\ \\ S \frac{}{n} = [ \: t \frac{}{1} + \: t \frac{}{n} ] \\ \\ d = t \frac{}{2} - t \frac{}{1}$