Comment
Share
Q)

# The wheel of a railway carriage is 40cm in diameter and makes 6 revolutions in a second;how fast is the train going?

$\begin{array}{1 1}(A)\;20cm/sec\\(B)\;24\pi cm/sec\\(C)\;24cm/sec\\(D)\;24cm/sec\end{array}$

Comment
A)
Toolbox:
• $r=\large\frac{d}{2}$
• Circumference =$2\pi r$
Given :
Diameter of the wheel =40cm
$\therefore$ Radius of the wheel =20cm
Circumference of the wheel =$2\pi r$
$\Rightarrow 2\pi \times 20$
$\Rightarrow 40\pi$cm
Number of revolutions made in 1 second =$6$
$\therefore$ Distance covered in 1 second=$40\pi\times 6$
$\Rightarrow 240\pi$cm
$\therefore$ Speed of the train =$24\pi$cm/sec
Hence (B) is the correct answer.

Comment
A)

Hello,

If you are preparing for a competitive exam, then its essential to follow some best study plans and strategies.

I’m preparing for Railway competitive exam by using top RRB Study Plan.

You can also take help from the above-mentioned link to get best results.