Given:the arc between 2 consecutive numbers on a clock. Each minute, the hour hand of the clock moves through 1/60 of such an arc. How many degrees does the hour hand move in 20 minutes?
Why is the solution 10 degrees?
1 arc is equal to 1/12th the distance around the clock.
so $\displaystyle 1 \mbox{ arc }=\frac{1}{12}360^\circ=30^\circ$
Lets start with what we know.
$\displaystyle \left( \frac{20 min}{1} \right)\left( \frac{1/60 arc}{1 min} \right)\left( \frac{30^\circ}{1 arc} \right) =10^\circ$