Question

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

Answer 1

Answer:

78 is the 16th term of the given AP

Explanation:

an=a+(n-1)d

78=3+(n-1)5

78-3=(n-1)5

75=(n-1)5

75/5=n-1

15=n-1

n-1=15

n=15+1

n=16

HOPE IT HELPS YOU

Answer 2

a (first term of A.P.) = 3

d (common difference) = 8-3 = 5

Let the nth term of A.P. be an.

an (nth term of an A.P.) = 78

an = a + ( n - 1 ) d

78 = 3 + ( n - 1 ) 5

78 - 3 = ( n - 1 ) 5

75 = ( n - 1 ) 5

75 / 5 = ( n - 1 )

n - 1 = 15

n = 15 + 1

n = 16

Therefore 16th term of the given A.P. is 78.