Question

If the sum of the first 14 terms of an AP is 1050 and its first term is 10 find the 20th term

Answer 1

n/2[2a+(n-1)d]=1050

= 14/2[20+13d]=1050

= 7[20+13d]=1050

= 20+13d=1050/7

= 20+13d=150

= 13d=130

d=10 

20th term = a+19d

                 = 10+19 * 10

                 = 10+190 

                 = 200

Answer 2

Sn=n/2[2a+(n-1)d]
here a=10,n=14 Sn=1050
S14=14/2[2(10)+(14-1)d]
1050=7(20+13d)
1050/7=20+13d
150=20+13d
150-20=13d
130=13d
d=130/13
d=10.
tn=a+(n-1)d
t20=10+(20-1)10
=10+19*10.
=10+190
t20 = 200