How many positive factors of 42 are not factors of 56?  Pick.
A) 1  B) 2  C) 3  D) four  E) 5
42=2*3*7.   So, total number of factors for 42 = 2*2 *2= 
<gadget id="calculator">2*2 *2</gadget>
<output>8</output>
8   factors for 42= 1,2,3,6,7,14,21 and 42   56=2*2*2*7   So, total number of factors for 56 = 4*2= 
<gadget id="calculator">4*2</gadget>
<output>8</output>
8   factors of 56= 1,2,4,7,8,14,28 and 56.   Factors same in 42 and 56 are 1,2,7 and 14.   Hence, answer will be four.
<result>D</result>
How many positive factors of 42 are not factors of 56?