Quantitative Aptitude Ques 1176
Question: If $ a+b+c=13, $ $ a^{2}+b^{2}+c^{2}=69, $ then find b $ ab+bc+ca. $
Options:
A) $ -50 $
B) $ 50 $
C) $ 69 $
D) $ 75 $
Show Answer
Answer:
Correct Answer: B
Solution:
- We know that, $ {{(a+b+c)}^{2}}=(a^{2}+b^{2}+c^{2})+2(ab+bc+ca) $ Now substituting the given values $ {{(13)}^{2}}=69+2(ab+bc+ca) $
$ \Rightarrow $ $ 169=69+2(ab+bc+ca) $
$ \Rightarrow $ $ \frac{169-69}{2}=ab+bc+ca $
$ \Rightarrow $ $ ab+bc+ca=50 $
BETA
