Question

sum of first and 5th term of an A P and fourth tourth term exceeds teice first term by 2.find the sum of first twenty terms​

Answer 1

Answer:

510

Explanation:

1. Sum of first term and fifth term of an ap is 18 that means a + (a+4d) = 18
2. Solving above equation we get a+ 2d = 9
3. Also given that fourth term exceeds twice the first term by 2
4. So that means a + 3d = 2a +2
5. From above equation we get relation for a and d
6. So we get a = 3d - 2
7. So using above relation in a + 2d = 9 we get value of d as 11/5 and a as 23/5
8. Sum.of n terms in AP is n/2[2a + (n-1)d]
9. For sum of twenty terms n = 20 and substituting values of a and d
10. So finally we get sum of twenty terms in AP is 510