Advertisements
Advertisements
प्रश्न
The sum of first 15 terms of an A.P. is 750 and its first term is 15. Find its 20th term.
उत्तर
Let a be the first term and d be the common difference.
Now, a = 15
Sum of first n terms of an AP is given by,
Sn = `"n"/(2)[2"a" + ("n" - 1)"d"]`
⇒ S15 = `(15)/(2)[2"a" + (15 - 1)"d"]`
⇒ 750 = `(15)/(2)(2"a" + 14"d")`
⇒ a + 7d = 50
⇒ 15 + 7d = 50
⇒ 7d = 35
⇒ d = 5
Now, 20th term = a20
= a + 19d
= 15 + 19 × 5
= 15 + 95
= 110.
संबंधित प्रश्न
Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149.
Find how many integers between 200 and 500 are divisible by 8.
Find the four numbers in A.P., whose sum is 50 and in which the greatest number is 4 times the least.
Find the sum of the first 25 terms of an A.P. whose nth term is given by an = 7 − 3n
Find the sum of first 20 terms of the sequence whose nth term is `a_n = An + B`
Find the sum of first 12 natural numbers each of which is a multiple of 7.
Is 184 a term of the AP 3, 7, 11, 15, ….?
What is the 5th term form the end of the AP 2, 7, 12, …., 47?
If an denotes the nth term of the AP 2, 7, 12, 17, … find the value of (a30 - a20 ).
The first term of an AP is p and its common difference is q. Find its 10th term.
Choose the correct alternative answer for the following question .
In an A.P. 1st term is 1 and the last term is 20. The sum of all terms is = 399 then n = ....
In an A.P. the first term is – 5 and the last term is 45. If the sum of all numbers in the A.P. is 120, then how many terms are there? What is the common difference?
Let there be an A.P. with first term 'a', common difference 'd'. If an denotes in nth term and Sn the sum of first n terms, find.
The first and last term of an A.P. are a and l respectively. If S is the sum of all the terms of the A.P. and the common difference is given by \[\frac{l^2 - a^2}{k - (l + a)}\] , then k =
The nth term of an A.P., the sum of whose n terms is Sn, is
x is nth term of the given A.P. an = x find x .
Q.19
If an = 3 – 4n, show that a1, a2, a3,... form an AP. Also find S20.
If the sum of first n terms of an AP is An + Bn² where A and B are constants. The common difference of AP will be ______.
In an A.P., if Sn = 3n2 + 5n and ak = 164, find the value of k.
