Advertisements
Advertisements
प्रश्न
The sum of 41 terms of an A.P. with middle term 40 is ______.
पर्याय
820
1640
2460
None of these
Advertisements
उत्तर
The sum of 41 terms of an A.P. with middle term 40 is 1640.
Explanation:
Since middle term = 40
`\implies` T21 = 40
`\implies` a + 20d = 40 ...(1)
We know that,
`S_n = n/2[2a + (n - 1)d]`
∴ `S_41 = 41/2[2a + 40d]`
= `41/2 xx 2[a + 20d]`
= 41 × 40 ...[Using (1)]
= 1640
APPEARS IN
संबंधित प्रश्न
In an AP given a3 = 15, S10 = 125, find d and a10.
Find the sum 2 + 4 + 6 ... + 200
In an A.P. the first term is 25, nth term is –17 and the sum of n terms is 132. Find n and the common difference.
Which term of the AP 21, 18, 15, ... is zero?
Find the sum of first n even natural numbers.
Write an A.P. whose first term is a and common difference is d in the following.
a = –1.25, d = 3
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.
Find the sum of those integers from 1 to 500 which are multiples of 2 or 5.
[Hint (iii) : These numbers will be : multiples of 2 + multiples of 5 – multiples of 2 as well as of 5]
Find the sum of all 11 terms of an A.P. whose 6th term is 30.
In a ‘Mahila Bachat Gat’, Kavita invested from the first day of month ₹ 20 on first day, ₹ 40 on second day and ₹ 60 on third day. If she saves like this, then what would be her total savings in the month of February 2020?
