Advertisements
Advertisements
Question
Find S2 for the A.P. 3,5,7,9,......
Solution
A.P. 3,5,7,9
Here, a = 3
d = t2 - t1 = 5 - 3
d = 2
Sn = `"n"/2[2"a" + ("n"-1)"d"]`
`"S"_2 = 2/2[2(3) + (2-1)2]`
= [6 + 1(2)]
= 6 + 2
= 8
APPEARS IN
RELATED QUESTIONS
Find the sum of the following.
`(1 - 1/n) +(1 -2/n) + (1- 3/n) +` ......up to n terms.
In an AP, the first term is 2, the last term is 29 and the sum of all the terms is 155. Find the common difference.
The sum of the first 9 terms of an AP is 81 and that of its first 20 terms is 400. Find the first term and common difference of the AP.
Two Aps have the same common difference. If the fist terms of these Aps be 3 and 8 respectively. Find the difference between the sums of their first 50 terms.
The sum first 10 terms of an AP is -150 and the sum of its next 10 terms is -550 . Find the AP.
An AP 5, 12, 19, .... has 50 term. Find its last term. Hence, find the sum of its last 15 terms.
The sum of the 4th and 8th terms of an AP is 24 and the sum of its 6th and 10th terms is 44. Find the sum of its first 10 terms.
The sum of fist m terms of an AP is ( 4m2 - m). If its nth term is 107, find the value of n. Also, Find the 21st term of this AP.
Sum of the first 14 terms of and AP is 1505 and its first term is 10. Find its 25th term.
In a school, students decided to plant trees in and around the school to reduce air pollution. It was decided that the number of trees that each section of each class will plant will be double of the class in which they are studying. If there are 1 to 12 classes in the school and each class has two section, find how many trees were planted by student. Which value is shown in the question?
Which of the following sequences are A.P.? If they are A.P. find the common difference.
2, 4, 6, 8, ...
Is the following sequences are A.P.? If is A.P. find the common difference.
0.3, 0.33, 0.333,...
Is the following sequences are A.P.? If is A.P. find the common difference.
Write the correct number in the given boxes from the following A. P.
–3, –8, –13, –18,...
Here t3 = 
, t2 = 
, t4 =
, t1 = 
,
t2 – t1 = 
, t3 – t2 = 
∴ a = 
, d = 
Write the correct number in the given boxes from the following A. P.
70, 60, 50, 40,...
Here t1 = 
, t2 = , t3 = ,...
∴ a = , d =
A = {1, 2, 3,4, 5}, B = {5, 6, 7} write AUB .
Write a trinomial of degree 7.
Find the sum of all numbers from 50 to 350 which are divisible by 4. Also, find the 15th term.
Find the first four terms in A.P. When a = 10 and d = 3.
