Question

Find 25th term of an ap where 11th term is 38 and 16 is 73

Answer 1

Answer:

136

Step-by-step explanation:

t11=38, n=11

tn=a+(n-1)×d

t11=a+(11-1)×d

38=a+10d

a+10d=38----------------(1)

t16=73, n=16

tn=a+(n-1)×d

t16=a+(16-1)×d

73=a+15d

a+15d=73----------------(2)

subtracting eqn(1) from (2)

a+15d=73

— a+10d=38

--------------------

5d=35

d=35/5

d=7

substituting d=7 in eqn (1)

a+10d=38

a+10×7=38

a+70=38

a =38-70

a=-32

now, a=-32, d=7, n=25, t25=?

tn=a+(n-1)×d

t25=-32+(25-1)×7

=-32+24×7

=-32+168

t25=136