Question

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

Answer 1

first term: 3

common difference: 5

so the equation would be:

aₙ = 3 + 5(n-1)

if aₙ = 78 then,

78 = 3 + 5(n-1)

5(n-1) = 78-3

5(n-1) = 75

n-1 = 75/5

n-1 = 15

n = 15 + 1

n = 16

answer: the 16th term of this AP is 78