I can still clearly recall the day Smart Joe joined our class. It was on
the first day of school after Christmas break. Everyone was crowding around
the new kid full of awe. He had a watch and he could even tell the time! The
teacher disturbed our conversation and made us take our seats. Luckily the
only free seat was next to mine, so Smart Joe sat down next to me. He told me
all kinds of fascinating stuff, but the real hit came on the next day during math.

We had been assigned some problems and I was trying to count on my fingers
properly, when I noticed that Smart Joe just took a look at his watch and
wrote down the answer. I asked him about his trick after school. His answer
was so brilliant and easy I still can't understand why the teacher didn't
teach math in his way. He counted on his watch instead of his fingers, which
of course makes it much faster.

This is why: if you have the problem 5 + 3 and you use your fingers, you
first have to count off five fingers, then three fingers, and in the end
you have to count how many fingers you have total.
If you use the face of a watch however, you just have to go to the five,
go three numbers further, and voila, you see right away that it adds up to
eight. For subtracting you just go counterclockwise. If you have the problem
9-2 you go to the nine, take two steps back, and you see it's seven. Much easier!

Test it yourself and solve the following probelms on Smart Joe's watch!