How many terms are there in the A.P. 15,21, 27, ................ , 279 ? |
35 40 45 55 |
45 |
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 |