0 Deepak BoraNewbie Asked: July 14, 20202020-07-14T23:21:08+05:30 2020-07-14T23:21:08+05:30In: CBSE Which term of the A.P. 3, 8, 13, 18, … is 78? 0 In this question the last term of A.P. is given, you have to find which term of A.P. this must be. This is question number 4 exercise 5.2,NCERT Maths solutions. a.p formulaarithmetic progressionnth term Share Facebook 1 Answer Voted Oldest Recent Deepak Bora Newbie 2020-09-22T14:59:51+05:30Added an answer on September 22, 2020 at 2:59 pm Solution: 11th term, a_{11} = 38 and 16th term, a_{16} = 73 We know , a_{n} = a + (n−1)d a_{11} = a + (11−1)d 38 = a + 10d ………………………………. (i) By the same way, a_{16} = a +(16−1)d 73 = a+15d ………………………………………… (ii) On subtracting eq. (i) from (ii), 35 = 5d d = 7 From eq. (i), 38 = a+10×(7) 38 − 70 = a a = −32 a_{31} = a +(31−1) d = − 32 + 30 (7) = − 32 + 210 = 178 So, 31st term is 178. 0 Reply Share Share Share on Facebook Share on Twitter Share on LinkedIn Share on WhatsApp Leave an answerLeave an answerCancel reply Featured image Select file Browse Add a Video to describe the problem better. Video type Youtube Vimeo Dailymotion Facebook Choose from here the video type. Video ID Put Video ID here: https://www.youtube.com/watch?v=sdUUx5FdySs Ex: "sdUUx5FdySs". Click on image to update the captcha. Save my name, email, and website in this browser for the next time I comment. Related Questions Question 1: Find the value of x for which (8x + 4), (6x – 2) and (2x + ... Problem 2: Find the indicated terms in each of the following sequences whose nth terms are(iii) an = ... Problem 1: Write the first terms of each of the following sequences whose nth term is: (i) an ... A kite is flying at a height of 75 meters from the ground level, attached to a string ... A tower stands vertically one the ground. From a point on the ground, 20 m away from the ...

Solution:11th term, a

_{11}= 38and 16th term, a

_{16}= 73We know ,

a

_{n}= a + (n−1)da

_{11}= a + (11−1)d38 = a + 10d ……………………………….

(i)By the same way,

a_{16}=a+(16−1)d73 =

a+15d…………………………………………(ii)On subtracting eq.

(i)from(ii),35 = 5

dd= 7From eq.

(i),38 =

a+10×(7)38 − 70 = a

a = −32

a

_{31}= a +(31−1) d= − 32 + 30 (7)

= − 32 + 210

= 178

So, 31st term is 178.