Home
Class 12
MATHS
If the sum of first 10 terms of an A.P. ...

If the sum of first 10 terms of an A.P. is 4 times the sum of its first 5 terms, then find the ratio of first term and common difference.

A

`(1)/(2)`

B

2

C

`(1)/(4)`

D

4

Text Solution

Verified by Experts

The correct Answer is:
A
According to the question, for AP
`S_(10)=4S_(5)`
`(10)/(2)(2a+9d)=4*(5)/(2)(2a+4d)[" by " S_(n)=(n)/(2)[2a+(n-1)d]]`
`10a+45d=20a+40d`
`implies 10a=5d " " implies (a)/(d)=(1)/(2)`
Promotional Banner

Similar Questions

Explore conceptually related problems

If the sum of first p terms of an A.P is equal to the sum of the first q terms , then find the first (p+q) terms .

7th term of an A.P. is 40. then the sum of the first 13 terms is

The sum of the first 8 terms of an A.P. is 100 and the sum of its first 19 terms is 551. Find the first term and the common difference of the AP.

If the sum of first n terms of an A.P. is cn^(2) , then the sum of squares of these n terms is :

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

The sum of first 7 terms of an AP is 63 and the sum of next 7 terms is 161. Find a_(28) .

The sum of first 14 terms of an AP is 1505 and its first term is 10. Find its tenth term.

IF the sum of three consecutive terms of an A.P. is 21, then first the first term.

If the sum of first 7 terms of an A.P is 49 and that of 17 terms is 289, find the sum of first n terms.

If the sum of first 7 terms of an AP is 49 and that of 17 terms is 289, find the sum of first n terms.