Question : 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 $\frac{7}{12}$. The numbers are:
Option 1: 20, 10 and 5
Option 2: 4, 2 and 1
Option 3: 36, 18 and 9
Option 4: 16, 8 and 4
Correct Answer: 4, 2 and 1
Solution :
Let us assume the third number is $x$.
Second number = 2$x$
First number = 2(2$x$) = 4$x$
Reciprocals of the three numbers = $\frac{1}{4x}, \frac{1}{2x}, \frac{1}{x}$
Average of the reciprocals = $\frac{7}{12}$
Sum of the reciprocals = $\frac{1}{4x}+\frac{1}{2x}+\frac{1}{x}=\frac{7}{4x}$
Average of reciprocals = $\frac{7}{4x} × \frac{1}{3} = \frac{7}{12x}$
So, $\frac{7}{12x} = \frac{7}{12}$
⇒ $x$ = 1
Hence, the numbers are 4, 2 and 1.
Related Questions
Know More about
Staff Selection Commission Multi Tasking ...
Answer Key | Cutoff | Selection Process | Preparation Tips | Eligibility | Application | Exam Pattern
Get Updates Brochure
Your Staff Selection Commission Multi Tasking Staff Exam brochure has been successfully mailed to your registered email id “”.
Upcoming Exams
Trending Articles around SSC MTS
