Question

An arithmetic sequence has a first term of 6.3 and a second term of 8.8 Which term has a value of 78.8?

Answer 1

First term [ a ] = 6.3

Common difference [ d ] = 8.8 - 6.3 = 2.5 

Using general term formula,

$t_{n} = a + (n-1)d$

78.8 = 6.3 + (n-1)*2.5

2.5*(n-1) = 72.5 [ Dividing both sides by 2.5 ]

n-1 = 29

n = 30

Hence, 78.8 is the 30th term in the arithmetic series.