Question

If the wheel of an engine of train $4\frac{2}{7}$ m in circumference makes seven revolutions in 4 seconds, then the speed of the train is

• A. $27$ km/h
• B. $27$ m/s
• C. $27$ m/h
• D. $27$ km/s

Answer 1

Answer: (A)

$27$ km/h

The distance travelled by the wheel in
7 revolutions $=4\frac{2}{7}\times 7m$
$=\frac{30}{7}\times 7m=30m$
Time taken is 4 seconds.
$\therefore Speed=\frac{distance}{time}=\frac{30}{4}m/sec$
$=\frac{15}{2}m/sec$
$\frac{15}{2}m/s=\frac{15}{2}\times \frac{18}{5}kmph$
$=3\times 9kmph$
$=27kmph$