Advertisements
Advertisements
प्रश्न
In an AP, given a = 7, a13 = 35, find d and S13.
In an A.P. (with usual notations): given a = 7, a13 = 35, find d and S13.
Advertisements
उत्तर
Given that, a = 7, a13 = 35
As an = a + (n − 1) d,
∴ a13 = a + (13 − 1) d
35 = 7 + 12d
35 − 7 = 12d
28 = 12d
d = `28/12`
d = `7/3`
sn = `n/2[a+a_n]`
S13 = `n/2[a+a_13]`
= `13/2[7+35]`
= `(13xx42)/2`
= 13 × 21
= 273
संबंधित प्रश्न
Ramkali saved Rs 5 in the first week of a year and then increased her weekly saving by Rs 1.75. If in the nth week, her week, her weekly savings become Rs 20.75, find n.
Find the sum of the following APs:
0.6, 1.7, 2.8, ... to 100 terms.
Find the sum of the odd numbers between 0 and 50.
The 7th term of an AP is –4 and its 13th term is –16. Find the AP.
If an denotes the nth term of the AP 2, 7, 12, 17, ..., find the value of (a30 - a20).
x is nth term of the given A.P. an = x find x .
Find the common difference of an A.P. whose first term is 5 and the sum of first four terms is half the sum of next four terms.
The sum of all two digit odd numbers is ______.
Find the sum of those integers from 1 to 500 which are multiples of 2 as well as of 5.
The sum of n terms of an A.P. is 3n2. The second term of this A.P. is ______.
