Try this trick
a few times, and you'll realize that it doesn't matter what numbers
you or your friend choose. The trick works no matter what.
In a two-digit number, the first number (the number on the left)
counts the number of sets of 10the 10s placeand
the second number (the number on the right) counts the number of
1sthe 1s place. The number 38, for example, has
three 10s and eight 1s.
All the math
you told your friend to do was just a roundabout way of putting
your friend's chosen number in the 10s place and your number
in the 1s place.
To see what's
really going on, let's go through the steps, one at a time.
Because it doesnt
matter what number your friend chooses, well just represent
it with a symbol, a .
This triangle could be any number between 1 and 9.
First, you told
your friend to double his or her number. Thats two times his
number, or two times .
You can write it mathematically like this: