Question

How many terms are there in ap 7 , 11 , 15......139.

Answer 1

Heya !!




AP = 7,11,15,...139



Here,


First term ( a ) = 7


Common difference ( d ) = 11 - 7 = 4





Tn = 139



a + ( n - 1 ) × D = 139




7 + ( n - 1 ) × 4 = 139



7 + 4n - 4 = 139



4n + 3= 139




4n = 136



n = 34.



Hence,


Number of terms = 34.

Answer 2

$we \: know \: that \\ an = a + (n - 1)d \\ where \: an = 139 \: \: a = 7 \: d = 11 - 7 \\ 139 = 7 + (n - 1)4 \\ 139 - 7 \div 4 = (n - 1) \\ 33 = (n - 1 )\\ n = 34 \: \\ n \: is \: number \: of \: terms$