# If a car is travelling at 21.8 kilometers per hour, how fast is that in millimeters per second?

Aug 16, 2015

I found: $6 \times {10}^{3} \frac{m m}{s}$

#### Explanation:

Consider that:
$21.8 k m = 21.8 \times 1000 m = 21800 m$
but $1 m = 1000 m m$ so:
$21800 m = 21800 \times 1000 = 2.18 \times {10}^{7} m m$

$1 h = 60 \min = 60 \times 60 = 3600 \sec$
So:
$21.8 \frac{k m}{h} = \frac{2.18 \times {10}^{7}}{3600} = 6 \times {10}^{3} \frac{m m}{s}$

Aug 16, 2015

$6055.5 \text{mm/s}$

#### Explanation:

We have $21.8 \text{km/hr}$

There are 1000m in 1 km so this gives us:

$21.8 \times 1000 \text{ ""m/hr}$

There are 60 min in 1 hour and 60 sec in 1 min so this gives us:

$\frac{21.8 \times 1000}{60 \times 60} \text{ ""m/s}$

There are 1000mm in 1m so this gives us:

$\frac{21.8 \times 1000 \times 1000}{60 \times 60} \text{ ""mm/s}$

$= 6055.5 \text{ " "mm/s}$