Hi I'm Mandy Schall, math specialist
Allegany County Public Schools.
Today I'm going to model addition of
decimals by using a number line. Today's
problem is Josh bought a coffee for one
dollar 39 cents and a dozen donuts for
six dollars 49 cents. How much money did
Josh spend? Since I am being asked how
much money he spent I know that I will
be adding. I will first write an equation
to match my story. One dollar and 39
cents plus six dollars and 49 cents
equals the total that Josh spent. I will
be drawing an open number line to model
the total amount spent by adding six
dollars and 49 cents to the one dollar
and 39 cents.
I will add six dollars or six wholes.
I now have seven dollars and 39 cents.
Next I will add 40 cents or 4 tenths.
I now have 7 dollars and 79 cents. Last I
will add 9 cents or 9 hundredths giving
me a total of seven dollars and
eighty-eight cents. Going back to my
equation one dollar and thirty-nine
cents plus six dollars and 49 cents
equals seven dollars and eighty-eight
cents. This is the mount that Josh spent
on coffee and donuts.
