Sports Watch the effect of the number of the outer ring

Just bought a Casio watch, is a pointer, the most outer ring has a circle of numbers, called Tachymeter (tachometer).

His role is to pass the count within 60s, which can be easily converted to a 1-hour metric. In other words, how many units of the current count are completed per hour.

Example 1:

For example, start the stopwatch, drive 2 km, with the 30s,30s corresponding to the outer ring number is 120, then the hour can walk 120*2 km,

That means the speed is 240 km/h.

The main point of course is to calculate the speed, but it can also be used to calculate the other, but the other data calculate how much one hours can be done little.

Example 2:

For example, eat dumplings, 60s ate 20 hours, 60s corresponding to the outer ring number is 60, then said one hours can eat 60*20=1200 dumplings, hehe, if you can continue to maintain the speed of the words.