How many natural numbers between 23 and 137 are divisible by 7?
Choices: A) 12 B) 17 C) 16 D) 13 E) 15
Solution : These numbers are 28, 35, 42,…., 133.   This is in A.P. in which a= 28, d=(35-28)= 
<gadget id="calculator">(35-28)</gadget>
<output>7</output>
7 and L=133.   Let the number of there terms be n. then, Tn=133   a+(n-1)d=133 by solving this we will get n=16.   Answer 16
<result>C</result>
How many natural numbers between 23 and 137 are divisible by 7?