Question

For an A.P. if first term is 30 and 30th term is 100 find S30

Answer 1

Step-by-step explanation:

first term of AP is = a = 30

30th term of AP is = a + 29d = 100

a + 29d = 100

30 + 29d = 100

29d = 100 - 30

29d = 70

d = 70/29

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

S30

$= \frac{30}{2} (2 \times 30 + (30 - 1) \frac{70}{29} ) \\ = 15(60 + (29 \times \frac{70}{29} ) \\ = 15(60 + 70) \\ = 15 \times 130 \\ = 1950$

sum of 30 terms is 1950

hope you get your answer