In A.P the difference between the 8th term and 4th term is 20,and the 8th term is one and half times the 4th term.Find the common difference, and the first term.

Answer 1

term(8) - term(4) = 20
a + 7d - a - 3d = 20
4d = 20
d = 5

term(8) = (3/2)(term(4))
a+7d = (3/2)(a+3d)
2a + 14d = 3a + 9d
5d = a
a = 25

a=25 ---> first term
d = 5

check:
sequence is:

25, 30, 35, 40, 45, 50, 55, 60, ..
term(8) = 60, term(4) = 20

is 60-40 = 20 ? yes
is 60 = (3/2)(40) ? yes