If p, q, and r are positive numbers such that (p/(p+q))(10) + (q/(p+q))(20)=r and if p<q which of the following could be the value of r?
Select
A) 10	B) 12	C) 15	D) 18	E) 30
The answer is D. For any positive p and q, r is a number between 10 and 20. Since p &lt; q, weight of 10 is inferior of weight of 20 -&gt; r is &gt; 15 -&gt; 18 is the answer.
<result>D</result>
If p, q, and r are positive numbers such that (p/(p+q))(10) + (q/(p+q))(20)=r and if p<q which of the following could be the value of r?