Question

If the sum of 5th term and 24th term of an A.P is 50 what is the sum of first 28 term

Answer 1

Answer:

700

Step-by-step explanation:

5th term = a + 4d

24th term = a + 23d

sum of 5th and 24th term is 50

a + 4d + a + 23d = 50

2a + 27d = 50

sum of first 28 terms

$= \frac{n}{2} (2a + (n - 1)d) \\ = \frac{28}{2} (2a + (28 - 1)d) \\ = \frac{28}{2} (2a + 27d) \\ = \frac{28}{2} \times 50 \: \: \: \: \: (2a + 27d = 50) \\ = 14 \times 50 \\ = 700$