Subject: General Aptitude · Chapter: Average · Exam: 2006 · Marks: · Difficulty:
Of four numbers whose average is 60, the first is one-fourth of the sum of the last three. The first number is
(a)15
(b)42
(c)45
(d)48
Answer
Answer (as printed): D
Explanation
Let the four numbers be $a, b, c$ and $d$ respectively. Then, $a=\frac{1}{4}(b+c+d) \Rightarrow b+c+d=4 a$. Also, $a+b+c+d=60 \times 4=240$ $$\Rightarrow a+4 a=240 \Rightarrow 5 a=240 \Rightarrow a=48 .$$ Hence, first number $=48$.
Explanation as extracted from the printed page; notation may be imperfect.