SOLUTION:
GOAL: You are being asked to find what digitsxandwrepresent.
STRATEGY: Use guess and test.
IMPLEMENTATION: Guess a few digits forxand see what works:
x¼ 4 : 4 x¼ 7 : 7 x¼ 5 : 5
475
þ 4 þ 7 þ 5
12 21 15Hencex¼5 andw¼1 is the correct answer.
EVALUATION: Notice that all the digits in the column are the same, that is,
they are all the same number. You must add three single digit numbers and
get the same number as the one’s digit of the solution. There are only two
possibilities: 0 and 5. Since the answer has two digits, 0 is disregarded.
Draw a Picture
Many times a problem can be solved using a picture, figure, or diagram. Also,
drawing a picture can help you to determine which other strategy can be used
to solve a problem.
EXAMPLE: Eight clothespins are placed on a clothesline at two-foot
intervals. How far is it from the first one to the last one?
SOLUTION:
GOAL: You are being asked to find the distance from the first clothespin to
the last one.
STRATEGY: Draw a figure and count the intervals between them; then
multiply by two.
IMPLEMENTATION: Solve the problem. See Figure 21-1.
LESSON 21 Using Other Strategies 259