Question

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

Answer 1

Answer:

a=3

d=5

An=a+(n-1)d

78=3+(n-1)5

78-5=(n-1)5

73=n-1*5

73/5=n-1

it is not possible to have 78

Step-by-step explanation:

Answer 2

The given sequence is 3,8,13,18,....78

a=3

d=5

last term=78

n=?

$\sf{t_n= a+(n-1)d}$

$\sf{→78=3+(n-1)5}$

$\sf{→78=3+5n-5}$

$\sf{→78=5n-2}$

$\sf{→5n=78+2}$

$\sf{→5n=80}$

$\sf{→n=\frac{80}{5}}$

$\sf{→n=16}$

The 16th term is 78.