Question

which term of AP 3 8 13 18 is 78​

Answer 1

Step-by-step explanation:

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Answer 2

$\bigstar$ Question:

Which term of the A.P. 3, 8, 13, 18, … is 78?

$\bigstar$ Solution:

As per the given information,

Given the A.P. series as 3, 8, 13, 18, …

First term, $a=3$

Common difference, d = $a_2 - a_1 = 8 - 3 = 5$

Let the $9^{th}$ term of given A.P. be 78. Now as we know,

$an = a+(n-1)d$

Therefore,

$78 = 3+(n -1)5\\75 = (n-1)5\\(n-1) = 15\\n = 16$

Hence, $16^{th}$ term of this A.P. is 78.