Video Transcript
Last week, Olivia bought one gallon
of milk for three dollars 50. This week, she bought two gallons
of milk for seven dollars 50. Is the total money she paid
proportional to the number of gallons?
So what we need to think about is
this word here “proportional” cause we has to decide “is the total money she paid
proportional to the number of gallons?” So if it is to be proportional and
we have one gallon is equal to three dollars 50, then if we wanted two gallons, the
price should be double. If we wanted four gallons, the
price should be multiplied by four. So let’s see if that’s the
case.
Well, if we’ve got one gallon for
three dollars 50 and we want two gallons, then what we need to do is multiply each
side of the equation by two. So one multiplied by two gives us
two gallons. Then, we have to multiply three
dollars 50 by two. Well, if we multiply three dollars
50 by two, we’re gonna get seven dollars. We can do that with some mental
arithmetic because if we multiply three by two, that will give us six. And if we multiply 50 cents by two,
that will give us one dollar. So six dollars plus one dollar
gives us seven dollars.
However, this wasn’t the price that
Olivia paid because Olivia bought two gallons of milk for seven dollars 50. So therefore, we can say and answer
the question “the relationship is not proportional.”
So the total money she paid is not
proportional to the number of gallons, because if it was, two gallons should have
cost seven dollars. However, two gallons cost seven
dollars 50.
