# Assistance on algebra word problem

• Mar 1st 2013, 02:57 PM
green11
Assistance on algebra word problem
The following is a method for multiplying 21x23 that relies on repeatedly doubling numbers (by adding them to themselves):

23
+23
----- 21=16+4+1
46 2
+46
-----
92 4
+92 368
----- 92
184 8 + 23
184 --------
----- 483
386 16

The answer, 483 to the multiplication problem 21*23, is shown on the bottom of the column on the right

Notice that, to use this repeated doubling method, you have to be able to only add; you don't need to know how to multiply.

A. Discuss and explain the method of repeated doubling. Address the following questions in your discussion:
I.What is the significance of the column of the numbers 2,4,8,16?
II.What is the significance of writing 21=16+4+1
III.How are the numbers 368, 92, and 23 chosen for the column on the right. Why do we add those numbers?

B.Use the method of repeated doubling to calculate 26*35. Show your work.

C.Use the method of repeated doubling to calculate 37*51. Show your work.
• Mar 1st 2013, 02:59 PM
green11
Re: Assistance on algebra word problem
368
92
+23
-----
486

I tried to move it some spaces over, but seem to got mixed with the problem