Advertisements
Advertisements
प्रश्न
In an A.P. a = 2 and d = 3, then find S12.
Advertisements
उत्तर
a = 2 and d = 3 ...[Given]
Since `S_n = n/2 [2a + (n - 1)d]`,
`S_12 = 12/2 [2(2) + (12 - 1)(3)]`
= 6[4 + 11(3)]
= 6(4 + 33)
= 6(37)
= 222
APPEARS IN
संबंधित प्रश्न
Find four numbers in A.P. whose sum is 20 and the sum of whose squares is 120
If (m + 1)th term of an A.P. is twice the (n + 1)th term, prove that (3m + 1)th term is twice the (m + n + 1)th term.
Find the sum of all even integers between 101 and 999.
How many terms of the A.P. : 24, 21, 18, ................ must be taken so that their sum is 78?
Find the 6th term form the end of the AP 17, 14, 11, ..., (–40).
Choose the correct alternative answer for the following question .
In an A.P. first two terms are –3, 4 then 21st term is ...
In an A.P. the 10th term is 46 sum of the 5th and 7th term is 52. Find the A.P.
Find the sum of all 2-digit natural numbers divisible by 4.
The sum of first n terms of an A.P. is 5n − n2. Find the nth term of this A.P.
If Sn denote the sum of n terms of an A.P. with first term a and common difference dsuch that \[\frac{Sx}{Skx}\] is independent of x, then
Two A.P.'s have the same common difference. The first term of one of these is 8 and that of the other is 3. The difference between their 30th term is
If \[\frac{5 + 9 + 13 + . . . \text{ to n terms} }{7 + 9 + 11 + . . . \text{ to (n + 1) terms}} = \frac{17}{16},\] then n =
Q.14
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:
Find the sum of first 1000 positive integers.
Activity :- Let 1 + 2 + 3 + ........ + 1000
Using formula for the sum of first n terms of an A.P.,
Sn = `square`
S1000 = `square/2 (1 + 1000)`
= 500 × 1001
= `square`
Therefore, Sum of the first 1000 positive integer is `square`
In an AP if a = 1, an = 20 and Sn = 399, then n is ______.
Find the sum:
`(a - b)/(a + b) + (3a - 2b)/(a + b) + (5a - 3b)/(a + b) +` ... to 11 terms
Find the sum of first 25 terms of the A.P. whose nth term is given by an = 5 + 6n. Also, find the ratio of 20th term to 45th term.
The sum of the 4th and 8th term of an A.P. is 24 and the sum of the 6th and 10th term of the A.P. is 44. Find the A.P. Also, find the sum of first 25 terms of the A.P.
Solve the equation:
– 4 + (–1) + 2 + 5 + ... + x = 437
