In 1992, a scoop of gelato could be purchased in Italy for 1200 lire. The same gelato would have cost $1.50 in the U.S. At the equivalent exchange rate between the lire and the dollar, how many dollars would be equivalent to 1,000,000 lire?
I'll set this up as a proportion. 1.50 is to 1,200 as X is to 1,000,000
Substitute a dividing line for "is to" 1.50 X
and substitute an equal sign for "as" –––––– = –––––––––
1,200 1,000,000
Now do the arithmetic. We called
it "cross multiplying" when I was in
school, a couple hundred years ago (1.50) • (1,000,000) = (1,200) • X
Divide both sides by 1,200 and
put the X on the left. You can leave (1.50) • (1,000,000)
it on the right if you want to, I just like X = ––––––––––––––––––
it better on the left 1,200
Breaking out the old calculator because I'm
to lazy to do the arithmetic manually and find X = 1,250 dollars, equivalent to a million lire
.
