Advertisements
Advertisements
प्रश्न
Which term of the A.P. 121, 117, 113 … is its first negative term?
[Hint: Find n for an < 0]
Advertisements
उत्तर
Given A.P. is 121, 117, 113 …
a = 121
d = 117 − 121
d = −4
an = a + (n − 1) d
= 121 + (n − 1) (−4)
= 121 − 4n + 4
= 125 − 4n
We have to find the first negative term of this A.P.
Therefore, an < 0
125 - 4n < 0
125 < 4n
`n > 125/4`
n > 31.25
Therefore, 32nd term will be the first negative term of this A.P.
संबंधित प्रश्न
In an AP: Given a = 5, d = 3, an = 50, find n and Sn.
If the sum of the first n terms of an AP is 4n − n2, what is the first term (that is, S1)? What is the sum of the first two terms? What is the second term? Similarly, find the 3rd, the 10th, and the nth terms.
Find the sum of first 15 multiples of 8.
The sum of the third and the seventh terms of an AP is 6 and their product is 8. Find the sum of first sixteen terms of the AP.
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.
Which term of the AP 3,8, 13,18,…. Will be 55 more than its 20th term?
If (3y – 1), (3y + 5) and (5y + 1) are three consecutive terms of an AP then find the value of y.
Choose the correct alternative answer for the following question .
If for any A.P. d = 5 then t18 – t13 = ....
The first term of an A. P. is 5 and the common difference is 4. Complete the following activity and find the sum of the first 12 terms of the A. P.
a = 5, d = 4, s12 = ?
`s_n = n/2 [ square ]`
`s_12 = 12/2 [10 +square]`
`= 6 × square `
` =square`
What is the sum of first 10 terms of the A. P. 15,10,5,........?
Ramkali would need ₹1800 for admission fee and books etc., for her daughter to start going to school from next year. She saved ₹50 in the first month of this year and increased her monthly saving by ₹20. After a year, how much money will she save? Will she be able to fulfil her dream of sending her daughter to school?
Which term of the sequence 114, 109, 104, ... is the first negative term?
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
Let the four terms of the AP be a − 3d, a − d, a + d and a + 3d. find A.P.
If the sum of the first four terms of an AP is 40 and that of the first 14 terms is 280. Find the sum of its first n terms.
The sum of the first 2n terms of the AP: 2, 5, 8, …. is equal to sum of the first n terms of the AP: 57, 59, 61, … then n is equal to ______.
The sum of first five multiples of 3 is ______.
Find the sum:
`4 - 1/n + 4 - 2/n + 4 - 3/n + ...` upto n terms
The nth term of an Arithmetic Progression (A.P.) is given by the relation Tn = 6(7 – n)..
Find:
- its first term and common difference
- sum of its first 25 terms
