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 = `"n"/2 ("t"_1 + "t"_"n")`
= `"n"/2 (1 + 149)`
= `"n"/2 xx 150`
= 75 n, where n = 75
APPEARS IN
संबंधित प्रश्न
Find the 9th term from the end (towards the first term) of the A.P. 5, 9, 13, ...., 185
How many terms of the A.P. 18, 16, 14, .... be taken so that their sum is zero?
Find the sum of the following APs.
`1/15, 1/12, 1/10`, ......, to 11 terms.
If the pth term of an A. P. is `1/q` and qth term is `1/p`, prove that the sum of first pq terms of the A. P. is `((pq+1)/2)`.
Which term of the AP 21, 18, 15, …… is -81?
Which term of the AP 3,8, 13,18,…. Will be 55 more than its 20th term?
First term and the common differences of an A.P. are 6 and 3 respectively; find S27.
Solution: First term = a = 6, common difference = d = 3, S27 = ?
Sn = `"n"/2 [square + ("n" - 1)"d"]` - Formula
Sn = `27/2 [12 + (27 - 1)square]`
= `27/2 xx square`
= 27 × 45
S27 = `square`
Kargil’s temperature was recorded in a week from Monday to Saturday. All readings were in A.P. The sum of temperatures of Monday and Saturday was 5°C more than sum of temperatures of Tuesday and Saturday. If temperature of Wednesday was –30° celsius then find the temperature on the other five days.
In an A.P., the sum of first ten terms is −150 and the sum of its next ten terms is −550. Find the A.P.
If `4/5` , a, 2 are three consecutive terms of an A.P., then find the value of a.
The sum of first 20 odd natural numbers is
The common difference of the A.P. is \[\frac{1}{2q}, \frac{1 - 2q}{2q}, \frac{1 - 4q}{2q}, . . .\] is
The common difference of the A.P.
Q.3
If the second term and the fourth term of an A.P. are 12 and 20 respectively, then find the sum of first 25 terms:
A merchant borrows ₹ 1000 and agrees to repay its interest ₹ 140 with principal in 12 monthly instalments. Each instalment being less than the preceding one by ₹ 10. Find the amount of the first instalment
The sum of first n terms of the series a, 3a, 5a, …….. is ______.
The sum of all two digit odd numbers is ______.
Show that the sum of an AP whose first term is a, the second term b and the last term c, is equal to `((a + c)(b + c - 2a))/(2(b - a))`
If the first term of an A.P. is p, second term is q and last term is r, then show that sum of all terms is `(q + r - 2p) xx ((p + r))/(2(q - p))`.
