Advertisements
Advertisements
प्रश्न
For an A.P., if t1 = 1 and tn = 149, then find Sn.
Activitry :- Here t1= 1, tn = 149, Sn = ?
Sn = `n/2 (square + square)`
= `n/2 xx square`
= `square` n, where n = 75
Advertisements
उत्तर
Here, t1= 1, tn = 149, Sn = ?
Sn = \[\frac{n}{2} (\boxed{t_1} + \boxed{t_n})\]
= `n/2 (1 + 149)`
= \[\frac{n}{2} \times \boxed{150}\]
= \[\boxed{75}\] n, where n = 75
APPEARS IN
संबंधित प्रश्न
Find the sum of the following APs:
–37, –33, –29, ... to 12 terms.
In a school, students thought of planting trees in and around the school to reduce air pollution. It was decided that the number of trees, that each section of each class will plant will be the same as the class, in which they are studying, e.g., a section of class I will plant 1 tree, a section of class II will plant 2 trees, and so on till class XII. There are three sections of each class. How many trees will be planted by the students?
Find the sum of first n odd natural numbers
Find the sum of the first 13 terms of the A.P: -6, 0, 6, 12,....
Find the sum 3 + 11 + 19 + ... + 803
Which term of the AP 3,8, 13,18,…. Will be 55 more than its 20th term?
Find the middle term of the AP 6, 13, 20, ..., 216.
The 8th term of an AP is zero. Prove that its 38th term is triple its 18th term.
If an denotes the nth term of the AP 2, 7, 12, 17, ..., find the value of (a30 - a20).
Find the sum of first n terms of an AP whose nth term is (5 – 6n). Hence, find the sum of its first 20 terms.
Write an A.P. whose first term is a and common difference is d in the following.
a = 6, d = –3
Find the sum of the first 15 terms of each of the following sequences having nth term as xn = 6 − n .
If Sn denotes the sum of first n terms of an A.P., prove that S12 = 3(S8 – S4).
Which term of the sequence 114, 109, 104, ... is the first negative term?
Write the nth term of the \[A.P. \frac{1}{m}, \frac{1 + m}{m}, \frac{1 + 2m}{m}, . . . .\]
Q.13
If the third term of an A.P. is 1 and 6th term is – 11, find the sum of its first 32 terms.
Find the sum of odd natural numbers from 1 to 101.
If the numbers n - 2, 4n - 1 and 5n + 2 are in AP, then the value of n is ______.
If the nth term of an AP is (2n + 1), then the sum of its first three terms is ______.
