Question

which term of the ap 3,6,13,18 is 78​

Answer 1

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Solution:

The formula for nth 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 16th term of the given AP.