Advertisements
Advertisements
प्रश्न
If the first term of an A.P. is 5, the last term is 15 and the sum of first n terms is 30, then find the value of n.
उत्तर
a = 5
Tn = l = 15
Sn = 30
n = ?
Sn = `n/2(a + l)`
⇒ 30 = `n/2(5 + 15)`
⇒ 60 = n × 20
⇒ 3 = n
APPEARS IN
संबंधित प्रश्न
In an A.P., if S5 + S7 = 167 and S10=235, then find the A.P., where Sn denotes the sum of its first n terms.
Check whether -150 is a term of the A.P. 11, 8, 5, 2, ....
Find the sum of the first 15 terms of each of the following sequences having the nth term as
yn = 9 − 5n
The first term of an A.P. is 5, the last term is 45 and the sum of its terms is 1000. Find the number of terms and the common difference of the A.P.
The sum of n natural numbers is 5n2 + 4n. Find its 8th term.
Find the sum of all natural numbers between 200 and 400 which are divisible by 7.
If the sum of n terms of an A.P. is 3n2 + 5n then which of its terms is 164?
The first three terms of an A.P. respectively are 3y − 1, 3y + 5 and 5y + 1. Then, y equals
The famous mathematician associated with finding the sum of the first 100 natural numbers is ______.
Find the sum of all even numbers from 1 to 250.
