In a set of integers, one-half of the numbers are multiples of 7 and one-third of the numbers are multiples of 3. If one-fifth of the numbers are multiples of both 3 and 7, then what percentage of the number are multiples of 7 but not multiples of 21? Pick one:
A) 9	B) 15	C) 30	D) 33.3	E) 60
Say there are 210 number in the set (LCM of 2, 3, 5, and 7).   Multiples of 7 = 1/2*210= 
<gadget id="calculator">1/2*210</gadget>
<output>105</output>
105;   Multiples of both 3 and 7, so multiples of 21= 1/5*210= 
<gadget id="calculator">1/5*210</gadget>
<output>42</output>
42.   Multiples of 7 but not 21= 105 - 42= 
<gadget id="calculator">105 - 42</gadget>
<output>63</output>
63.   The percentage= 63/210 = 3/10.   Answer: 30.
<result>C</result>
In a set of integers, one-half of the numbers are multiples of 7 and one-third of the numbers are multiples of 3. If one-fifth of the numbers are multiples of both 3 and 7, then what percentage of the number are multiples of 7 but not multiples of 21?