Question

Find the sum of all numbers from 150 to 200 which are divisible by7​

Answer 1

Step-by-step explanation:

The sum is 1225

Solution : 

The numbers from 150 to 200 divisible by 7 are 154,161 ,168,…., 196

Here, a=154,d=7a=154,d=7 and tn=196tn=196

tn=a+(n−1)dtn=a+(n-1)d …(Formula )

∴196=154+(n−1)×7∴196=154+(n-1)×7 …(Substituting the values )

∴196−154=(n−1)×7∴196-154=(n-1)×7

∴427=n−1∴427=n-1 ∴n−1=6∴n-1=6 ∴n=7∴n=7

Now, we find the sum of 7 numbers.

Sn=n2[t1+tn]Sn=n2[t1+tn] ...(Formula )

=72[154+196)=72[154+196)

=72×350=72×350

=7×175=7×175

=1225