Advertisements
Advertisements
प्रश्न
Find t21, if S41 = 4510 in an A.P.
Advertisements
उत्तर
For an A.P., let a be the first term and d be the common difference.
S41 = 4510 ......[Given]
Since Sn = `"n"/2 [2"a" + ("n" - 1)"d"]`,
S41 = `41/2 [2"a" + (41 - 1)"d"]`
∴ 4510 = `41/2 (2"a" + 40"d")`
∴ 4510 = `41/2 xx 2 ("a" + 20"d")`
∴ 4510 = 41(a + 20d)
∴ a + 20d = `4510/41`
∴ a + 20d = 110 .....(i)
Now, tn = a + (n – 1)d
∴ t21 = a + (21 – 1)d
= a + 20d
∴ t21 = 110 ......[From (i)]
APPEARS IN
संबंधित प्रश्न
If the mth term of an A.P. is 1/n and the nth term is 1/m, show that the sum of mn terms is (mn + 1)
In an AP given a3 = 15, S10 = 125, find d and a10.
Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149.
Show that a1, a2,..., an... form an AP where an is defined as below:
an = 3 + 4n
Also, find the sum of the first 15 terms.
Find how many integers between 200 and 500 are divisible by 8.
Three numbers are in A.P. If the sum of these numbers is 27 and the product 648, find the numbers.
Find the sum of the first 25 terms of an A.P. whose nth term is given by an = 2 − 3n.
Which term of the AP 3,8, 13,18,…. Will be 55 more than its 20th term?
If the pth term of an AP is q and its qth term is p then show that its (p + q)th term is zero
Find four numbers in AP whose sum is 8 and the sum of whose squares is 216.
Which term of the AP 21, 18, 15, … is zero?
Choose the correct alternative answer for the following question .
If for any A.P. d = 5 then t18 – t13 = ....
Write the sum of first n even natural numbers.
If the first, second and last term of an A.P. are a, b and 2a respectively, its sum is
The common difference of an A.P., the sum of whose n terms is Sn, is
If the first term of an A.P. is a and nth term is b, then its common difference is
Q.5
In a ‘Mahila Bachat Gat’, Sharvari invested ₹ 2 on first day, ₹ 4 on second day and ₹ 6 on third day. If she saves like this, then what would be her total savings in the month of February 2010?
First four terms of the sequence an = 2n + 3 are ______.
The sum of n terms of an A.P. is 3n2. The second term of this A.P. is ______.
