Subject: General Aptitude · Chapter: Average · Exam: · Marks: · Difficulty:
Of the three numbers, the first is twice the second and the second is twice the third. The average of the reciprocal of the numbers is $\frac{7}{72}$. The numbers are :
(a)16, 8, 4
(b)20, 10, 5
(c)24, 12, 6
(d)36, 18, 9
Answer
Answer (as printed): C
Explanation
Let the third number be $x$. Then, second number $=2 x$. First number $=4 x$. $$\therefore \frac{1}{x}+\frac{1}{2 x}+\frac{1}{4 x}=\left(\frac{7}{72} \times 3\right) \text { or } \frac{7}{4 x}=\frac{7}{24} \text { or } 4 x=24 \text { or } x=6 .$$ So, the numbers are 24, 12 and 6.
Explanation as extracted from the printed page; notation may be imperfect.