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