Question

A car travels 100 meters in 5 seconds. What is the speed of the car?

speed = distance over time; 1 mile = 1609 meters

8.9 miles per hour
16 miles per hour
20 miles per hour
44.7 miles per hour

Answer 1

\(\dfrac{100~m}{5~sec} \)

How do you convert seconds to hours?

Answer 2

speed=100/5 m/s=20 m/s
now convert to

Answer 3

im sooo confused still

Answer 4

1 meter=1/1609 miles

Answer 5

1 sec=1/3600 hours

Answer 6

Since 1 mile = 1609 m, we have the conversion factors:

\(\dfrac{1609~m}{1~mile} = \dfrac{1~mile}{1609~m} = 1\)

We will use the conversion factor that will cancel out meters and will leave miles.

We still need to convert from seconds to hours.

Answer 7

We can go through minutes.

\(60 ~sec = 1 ~min\) gives us \(\dfrac{60~sec}{1~min} = \dfrac{1~min}{60~sec} = 1\)

\(60 ~min = 1 ~hour\) gives us \(\dfrac{60~min}{1~hour} = \dfrac{1~hour}{60~min} = 1\)

Answer 8

im still lost

Answer 9

Now we just pick the conversion factors that will cancel the units we don't want and will leave the units we want.

Answer 10

I'm explaining step by step.
We already have all the conversion factors we need above.
Now we start with the given part: 100 m in 5 sec.

\(\dfrac{100 ~m}{5~sec} \)

Answer 11

Now we apply each conversion factor.
We need to eliminate meters and end up with miles.

\(\dfrac{100 ~m}{5~sec} \times \dfrac{1~mile}{1609~m}\)

meters cancels meters, and we now have miles.

Answer 12

44.7 miles per hour ????

Answer 13

Now we eliminate seconds and get minutes.

\(\dfrac{100 ~m}{5~sec} \times \dfrac{1~mile}{1609~m} \times \dfrac{60~sec}{1~min}\)

Answer 14

Now we eliminated seconds and ended up with minutes.
We just have one more conversion to do, to eliminate minutes and end up with hours.

Answer 15

\(\dfrac{100 ~m}{5~sec} \times \dfrac{1~mile}{1609~m} \times \dfrac{60~sec}{1~min}
\times \dfrac{60~min}{1~hour} = 44.7 ~\dfrac{miles}{hour}\)