Question

if 5th term of an ap is 12.5 and 8th term is 20,find d

Answer 1

Answer:

d = 2.5

Step-by-step explanation:

The 5th term of an AP,

5th term = a + ( n-1 ) d

12.5 = a + ( 5-1 ) d

12.5 = a + 4d

4d = 12.5 - a _ ( I )

The 8th term of an AP,

8th term = a + ( n-1 ) d

20 = a + ( 8-1 ) d

20 = a + 7d

20 = a + 4d + 3d

20 = a + 12.5 - a + 3d ....from ( I )

20 = 12.5 + 3d

3d = 20 - 12.5

d = 7.5 / 3

d = 2.5