Advertisements
Advertisements
प्रश्न
The sum of first 16 terms of the AP: 10, 6, 2,... is ______.
विकल्प
–320
320
–352
–400
Advertisements
उत्तर
The sum of first 16 terms of the AP: 10, 6, 2,... is –320.
Explanation:
Given, AP is 10, 6, 2,...
Here,
First term a = 10,
Common difference,
d = – 4
∴ S16 = `16/2[2a + (16 - 1)d]` ...`[∵ S_n = n/2[2a + (n - 1)d]]`
= 8[2 × 10 + 15(– 4)]
= 8(20 – 60)
= 8(– 40)
= – 320
APPEARS IN
संबंधित प्रश्न
In an AP given d = 5, S9 = 75, find a and a9.
If the sum of first m terms of an A.P. is the same as the sum of its first n terms, show that the sum of its first (m + n) terms is zero
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)`.
In an A.P., if the first term is 22, the common difference is −4 and the sum to n terms is 64, find n.
Find the sum of all multiples of 7 lying between 300 and 700.
The 24th term of an AP is twice its 10th term. Show that its 72nd term is 4 times its 15th term.
How many three-digit numbers are divisible by 9?
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 = –1.25, d = 3
What is the sum of first 10 terms of the A. P. 15,10,5,........?
Two cars start together in the same direction from the same place. The first car goes at uniform speed of 10 km h–1. The second car goes at a speed of 8 km h–1 in the first hour and thereafter increasing the speed by 0.5 km h–1 each succeeding hour. After how many hours will the two cars meet?
Q.1
Q.7
Obtain the sum of the first 56 terms of an A.P. whose 18th and 39th terms are 52 and 148 respectively.
The sum of first 15 terms of an A.P. is 750 and its first term is 15. Find its 20th term.
The middle most term(s) of the AP: -11, -7, -3,.... 49 is ______.
If the nth term of an AP is (2n +1), then the sum of its first three terms is ______.
Find the sum of first 'n' even natural numbers.
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))`.
Three numbers in A.P. have the sum of 30. What is its middle term?
