Question

In a $800$ m race, $A$ defeated $B$ by $15$ seconds. If $A$'s speed was $8$ km/hour. What was $B$'s speed?

• A. $7\frac{17}{25}$ km/hour
• B. $2\frac{5}{18}$ km/hour
• C. $2\frac{5}{21}$ km/hour
• D. $7\frac{18}{25}$ km/hour

Answer 1

The correct option is A $7\frac{17}{25}$ km/hour

Given, Distance ($D$) $=$ $800$ m, Speed of $A=$ $V_A=8$ $km/hour$ and speed of $B=$ $V_B$

Time taken by $A$ to finish the race $=\frac{0.8}{8}=0.1$ hours $=6$ minutes $=360$ seconds.

Time taken by $B$ $=360+15=375$ seconds

Speed of $B$ $=\frac{800}{375}$ $m/s$ or $\frac{192}{25}$ $km/hour$ ....$[1m/s=\frac{18}{5}$$km/hour]$