Question

Eind the sum of all ineqers between 1 to 50
which are not divisible by 3.​

Answer 1

Answer:

Here, a=3, d=3 and tn=48

tn=a+(n-1)d

48=3+(n-1)×3

3(n-1)=48-3

3(n-1)=45

(n-1)=45/3

(n-1)=15

n=16

$\sf{S_{n}=\dfrac{n}{2}[t_{1}+t_{n}]}$

$\sf{S_{16}=\dfrac{16}{2}[3+48]}$

$\sf{S_{16}=8\times51}$

$\sf{S_{16}=408}$

The sum of all ineqers between 1 to 50

which are not divisible by 3 is 408.