Question

If the common difference
of an AP is -2, the first term is
100 and last term is -10 then
its sum is​

Answer 1

Answer:

use an=a+(a2-a1)×d

hope u use this formula to calculate the answer

Answer 2

Answer:

2520

Step-by-step explanation:

given c.d. = -2

1st term = 100 and last term = -10

Sum of all terms in a finite AP with the last term as 'l' ⇒ n/2(a + l)  ......(1)

nth term of AP ⇒ an = a + (n – 1) × d

-10 = 100 (n-1) (-2)  ⇒ 2n = 100 + 2 +10  ⇒ n = 56

∴  from(1) 56/2(100-10)  ⇒ sum of all terms in a finite AP = 2520