A person travelled from his house to office at 10km/hr and office to house at 90km/hr. Then find the average speed?	Choose the correct choice from the following
A) 15km/hr	B) 18km/hr	C) 25km/hr	D) 28km/hr	E) 33km/hr
Average speed = (2*10*90)/(10+90)= 
<gadget id="calculator">(2*10*90)/(10+90)</gadget>
<output>18</output>
18km/hr
Answer is 18km/hr
<result>B</result>
A person travelled from his house to office at 10km/hr and office to house at 90km/hr. Then find the average speed?