Question

The fourth term of an Ap is 10. If eleventh term is one more three times of the fourth term find the sum of its 25 terms.



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Answer 1

Answer:

925

Explanation:

t4=10

a+3t=10....(1)

t11=1+3*10

a+10d= 31....(2)

subtract 1 from 2

7d=21

d=3

hence a=1

s25=n/2(2a+(n-1) d) =25/2(2+24*3)=25/2*74

=25*37=925