Which term of the AP : 3, 8, 13, 18, . . . ,is 78?

Solution:

The formula for n^th term of an AP is aₙ = a + (n - 1) d

The given arithmetic progression is 3, 8, 13, 18, ...

First term: a = 3

Second term: a + d = 8

Common difference: d = 8 - 3 = 5

aₙ = a + (n - 1) d 

aₙ = 78, n = ?

3 + (n - 1) 5 = 78

5(n - 1) = 78 - 3

n - 1 = 15

n = 16

78 is the 16^th term of the given AP.

☛ Check: NCERT Solutions for Class 10 Maths Chapter 5

Video Solution:

Which term of the AP : 3, 8, 13, 18, . . . ,is 78?

NCERT Solutions Class 10 Maths Chapter 5 Exercise 5.2 Question 4

Summary:

78 is the 16^th term of the AP 3, 8, 13, 18, ...

☛ Related Questions:

• Find the number of terms in each of the following APs: i) 7, 13, 19,..., 205 ii) 18, 15 ½, 13 ,..., - 47.
• Check Whether -150 is a term of the AP 11, 8, 5, 2 …..
• Find the 31st term of an AP whose 11th term is 38 and the 16th term is 73.
• An AP consists of 50 terms of which the 3rd term is 12 and the last term is 106. Find the 29th term.