Sum of products of three numbers taken two at a time is 131. Sum of squares of the three numbers is 138. What is the sum of the three numbers?	Choose the correct choice
A) 25
B) 30
C) 20
D) 22
E) 21
Explanation:   All the data given in the question points to the equation mentioned below:   Considering the three numbers to be a,b and c:   (a+b+c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca   Accordingly, substitute for a, b and c and solve:   =&gt; a2+b2+c2= 138, ab+bc+ac = 131. Thus, 2(ab+bc+ac)= 2*131= 
<gadget id="calculator">2*131</gadget>
<output>262</output>
262   (a+b+c)2= 138+262= 
<gadget id="calculator">138+262</gadget>
<output>400</output>
400.   Therefore, a+b+c= 20   ANSWER: 20
<result>C</result>
Sum of products of three numbers taken two at a time is 131. Sum of squares of the three numbers is 138. What is the sum of the three numbers?