How many natural numbers are there between 23 and 100 which are exactly divisible by 6 ?  Choose the most appropriate option
A) 5
B) 6
C) 13
D) 18
E) 24
Explanation:   Required numbers are 24, 30, 36, 42, ..., 96   This is an A.P. in which a = 24, d = 6 and l = 96   Let the number of terms in it be n.   Then tn = 96 a + (n - 1)d = 96   24 + (n - 1) x 6 = 96   (n - 1) x 6 = 72   (n - 1) = 12   n = 13   Required number of numbers = 13.   ANSWER 13
<result>C</result>
How many natural numbers are there between 23 and 100 which are exactly divisible by 6 ?