Question

for an A.P.,if S10=150andS9=126,t10=?

Answer 1

S10 = 150
10/2 [2a + 9d ] = 150

2a + 9d = 30 ....... (i)

S9 = 126
9/2 [2a + 8d] = 126

2a + 8d = 28 ..........(ii)

Subtract (i) and (ii)

d= 2

put in (ii)

2a + 8 (2) = 28
2a = 12

a = 6

t10 = a +9d
= 6 +9 (2)
= 6 + 18
= 24