Advertisements
Advertisements
प्रश्न
Choose the correct alternative answer for the following question .
In an A.P. first two terms are –3, 4 then 21st term is ...
पर्याय
-143
143
137
17
उत्तर
It is given that,
a = –3
a2 = 4
We know that,
\[a_2 = a + \left( 2 - 1 \right)d\]
\[ \Rightarrow 4 = - 3 + d\]
\[ \Rightarrow d = 7\]
Now,
\[a_{21} = a + \left( 21 - 1 \right)d\]
\[ = - 3 + 20\left( 7 \right)\]
\[ = - 3 + 140\]
\[ = 137\]
APPEARS IN
संबंधित प्रश्न
If Sn1 denotes the sum of first n terms of an A.P., prove that S12 = 3(S8 − S4).
If Sn denotes the sum of first n terms of an A.P., prove that S30 = 3[S20 − S10]
Find the sum given below:
–5 + (–8) + (–11) + ... + (–230)
Which term of the A.P. 121, 117, 113 … is its first negative term?
[Hint: Find n for an < 0]
Find the sum of the following arithmetic progressions:
−26, −24, −22, …. to 36 terms
Find the sum of the first 25 terms of an A.P. whose nth term is given by an = 2 − 3n.
Find the sum of the first 22 terms of the A.P. : 8, 3, –2, ………
Which term of the AP `20, 19 1/4 , 18 1/2 , 17 3/4 ` ,..... is the first negative term?
If (3y – 1), (3y + 5) and (5y + 1) are three consecutive terms of an AP then find the value of y.
If (2p – 1), 7, 3p are in AP, find the value of p.
If Sn denotes the sum of first n terms of an A.P., prove that S12 = 3(S8 − S4).
Two cars start together in the same direction from the same place. The first car goes at uniform speed of 10 km h–1. The second car goes at a speed of 8 km h–1 in the first hour and thereafter increasing the speed by 0.5 km h–1 each succeeding hour. After how many hours will the two cars meet?
Find second and third terms of an A.P. whose first term is – 2 and the common difference is – 2.
For an A.P., If t1 = 1 and tn = 149 then find Sn.
Activitry :- Here t1= 1, tn = 149, Sn = ?
Sn = `"n"/2 (square + square)`
= `"n"/2 xx square`
= `square` n, where n = 75
Determine the sum of first 100 terms of given A.P. 12, 14, 16, 18, 20, ......
Activity :- Here, a = 12, d = `square`, n = 100, S100 = ?
Sn = `"n"/2 [square + ("n" - 1)"d"]`
S100 = `square/2 [24 + (100 - 1)"d"]`
= `50(24 + square)`
= `square`
= `square`
Shubhankar invested in a national savings certificate scheme. In the first year he invested ₹ 500, in the second year ₹ 700, in the third year ₹ 900 and so on. Find the total amount that he invested in 12 years
If the numbers n - 2, 4n - 1 and 5n + 2 are in AP, then the value of n is ______.
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is ______.
Which term of the AP: –2, –7, –12,... will be –77? Find the sum of this AP upto the term –77.
If the last term of an A.P. of 30 terms is 119 and the 8th term from the end (towards the first term) is 91, then find the common difference of the A.P. Hence, find the sum of all the terms of the A.P.
