Is 62.5 kilometers per hour fast or slow for an average car?

Here is how you do arithmetic in your head. You memorize fractions:
1/2 = 0.5
1/3 = 0.333
1/4 = 0.25
1/5 = 0.2
1/6 = 0.166
1/7 = 0.144
1/8 = 0.125
1/9 = 0.111
1/10 = 0.1
1/11 = 0.91
1/12 = 0.833
and so on.

100 kilometers is 62 miles. So 62.5 kilometers is something over 36 miles (62.5 km x 0.62 = 38.75 miles) and that is just a normal speed for driving through town. It has nothing to do with "average car", it depends on the neighborhood: a residential area would be 25 mph or 40 kph, a business district would be 35 mph or 56 kph, a four lane road with fences on both sides would be 45 mph or 72 kph.

In science fiction you often here someone mention "click". That is a kilo kilometer, one million meters, or 620 miles.