Advertisements
Advertisements
प्रश्न
The first and the last terms of an A.P. are 34 and 700 respectively. If the common difference is 18, how many terms are there and what is their sum?
Advertisements
उत्तर
Let there be n terms in this A.P.
First term a = 34
Common difference d = 18
Last term l = 700
`=>` a + (n – 1)d = 700
`=>` 34 + (n – 1) × 18 = 700
`=>` (n – 1) × 18 = 666
`=>` n – 1 = 37
`=>` n = 38
Sum of first n terms = `n/2 [a + l]`
= `38/2 [34 + 700]`
= 19 × 734
= 13946
संबंधित प्रश्न
The sum of the first p, q, r terms of an A.P. are a, b, c respectively. Show that `\frac { a }{ p } (q – r) + \frac { b }{ q } (r – p) + \frac { c }{ r } (p – q) = 0`
The first and last terms of an AP are 17 and 350, respectively. If the common difference is 9, how many terms are there, and what is their sum?
Find the sum of the first 15 terms of each of the following sequences having the nth term as
`a_n = 3 + 4n`
How many three-digit natural numbers are divisible by 9?
Choose the correct alternative answer for the following question .
In an A.P. first two terms are –3, 4 then 21st term is ...
The sum of the first n terms of an A.P. is 3n2 + 6n. Find the nth term of this A.P.
Obtain the sum of the first 56 terms of an A.P. whose 18th and 39th terms are 52 and 148 respectively.
Find t21, if S41 = 4510 in an A.P.
The sum of the first 15 multiples of 8 is ______.
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.
