3295263856329

Multiplication 33
Figure 3-6
It doesn’t matter which part of the problem we do
first. We get the same answer either way.
USING YOUR CALCULATOR TO VERIFY THIS PROCESS
When you have a digital calculator, it is easy to punch in one number, then the “times
sign” (), then the other number, and finally the equals sign (). Bingo, you have the
answer, all complete! But this doesn’t help you see how the calculator actually does the
work. Figure 3-7 can help you see that for the product 3,542 27.
Suppose we have a calculator with a single memory, which is the simplest type.
Multiplying 7 by 2 gives us 14, which we enter in memory with a button labeled
something like “MS” for “memory save.” Then we multiply 7 by 40, which gives us
280. Next, we add this number to the 14 with the “M” or “memory add” button. We
can read what we already have by pressing the “MR” or “memory recall” button.
Finish multiplying by 7 and then press the MR button to display the first partial product
of 24,794.
After that we can go on and multiply by 20. With a single memory, we don’t see the
“times 20” part separately, as we do in longhand. But the final answer is the same. If
you have a calculator with more than one memory, you can store each partial product
in a separate memory and then add the contents of the two memories.
Figure 3-7
Here is how you
can use a calculator
to find the product
3,542 27 in
two parts, as shown
previously by the
longhand method.