How many terms are there in the A.P. 15,21, 27, ................ , 279 ?
Answer & explanation
Correct answer: option 3
A.P. = 15,21, 27, ................ , 279
an = a + ( n - 1 )d
a = 1st term , n = number of terms , d = common difference
an = last term
279 = 15 + ( n - 1 )6
264 = ( n - 1 )6
( n - 1 ) = 44
n = 45
The correct answer is option (3) : 45