Finding the time from disance and speed

Question

$2$ bikes $A$ and $B$ took part in a $1.5$ km Race. $A$ travel at $100$ km/h. $B$ travel at $120$ km/h. After how many minutes/seconds Bike $A$ will reach finishing point after Bike $B$ finishes?

--the answer is given as $3$ minutes or$0.05$ hours. I am unable to get this answer. Could someone help me out here?

Answer 1

Hint: Recall that $\textrm{time}\times\textrm{rate}=\textrm{distance}$, so this means that $\textrm{time} = \textrm{distance}\div\textrm{rate}$.

This will let you compute a time for each biker. Assuming they started at the same instant, you can find the difference in their times by just subtracting.

Don't forget to convert the times to the same units for computation.

Answer 2

Since $distance=rate*time$, $time=distance*\frac{1}{rate}$.

So the time it takes $A$ to complete the race is $1.5\ Km*\frac{1hr}{100Km}=.015\ hours$.

Similarly, the time it takes $B$ is $1.5\ Km*\frac{1hr}{120Km}=.0125\ hours$.

Consequently, $A$ arrives $.015-.0125=.0025 \ hours$ later.

$.0025\ hours *\frac{60\ min}{1\ hour}*\frac{60\ seconds}{1\ min}=9\ seconds$.

Answer 3

$Time$ = $\frac{Distance}{Speed}$

For biker A Time = $\frac{1.5}{100}$ = $.015$ hours or $54$ sec.

For biker B Time = $\frac{1.5}{120}$ = $.0125$ hours or $45$ sec.

So difference is $9$ sec.