Question

Find the sum of the AP: 1,2,3 ....10​

Answer 1

Step-by-step explanation:

$sn = \frac{n}{2} (a + (n - 1)d)$

here,

a=1

d=1

n=2

$= \frac{10}{2} (1 + (10 - 1)1)$

$= 5(1 + (9)1)$

$= 5(1 + 9)$

$= 5 \times 10$

$= 50$

Answer 2

Step-by-step explanation:

here

a=1

d=2-1=1

an=10

sn=n/2(2a+(n-1)d)

S10=10/2(2×1+(10-1)d)

S10=5(2+(10-1)1)

=5(2+10-1)

=5(1+10)

=5×11

=55