wiz-icon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

The sum of first 10 term of an A.P is one third of sum of next 10 term. If first term is 5.. Find the sum of its first 30 terms

Open in App
Solution

Given,

a=5

S10=5[10+9d]

S20=10[10+19d]

S10=13(S20S10)

5[10+9d]=13{10[10+19d]5[10+9d]}

15[10+9d]={10[10+19d]5[10+9d]}

150+135d={100+190d+5045d}

150+135d=50+145d

100=10d

d=10

S30=302[2(5)+(301)(10)]

=15[10+29(10)]

=4500

flag
Suggest Corrections
thumbs-up
0
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Sum of n Terms of an AP
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon