Question

Find the sum of natural numbers from $1$ to $140$ which are divisible by $7$.

• A. $1470$
• B. $2344$
• C. $1234$
• D. $2334$

Answer 1

The correct option is A $1470$

$1$ to $140$

$7\left(1\right)+7\left(2\right)+7\left(3\right).....7\left(20\right)$

Sum of n natural numbers$=\frac{n(n+1)}{2}$

$=7(1+2+\mathrm{3....20})$

$=\frac{7\times 20\times 21}{2}$

$=7\times 10\times 21$

$=1470$