Question

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

Answer 1

Answer:

an = a+(n-1)d

an=78

a=3

d= 8-3=5

so

78=3+(n-1)5

78=3+5n-5

78-3+5=5n

83-3=5n

80=5n

80÷5=n

16=n

so it is 16th term of the AP