ABC26GN0201 · Number System

Subject: General Aptitude · Chapter: Number System · Exam: · Marks: · Difficulty:

If $a=7, b=5, c=3$, then the value of $a^{2}+b^{2}+$ $c^{2}-a b-b c-c a$ is

(a)- 12

(b)0

(c)8

(d)12

Answer

Answer (as printed): D

Explanation

$$\begin{aligned} \left(a^{2}+b^{2}+c^{2}-a b-b c-c a\right) & =(a+b+c)^{2}-3(a b+b c+c a) \\ & =(7+5+3)^{2}-3(35+15+21) \\ & =(15)^{2}-3 \times 71 \\ & =(225-213)=12 . \end{aligned}$$

Explanation as extracted from the printed page; notation may be imperfect.

Open in whiteboard · Browse this chapter in the app