Introduction:
 Mental Math
o Multiplication by 0.1, 0.01, and 0.001
o Show them how the numbers scale downwards
o Establish the patterns (use a place value chart)
 3x1=3, 3x0.1=0.3, 3x0.01=0.03, 3x0.001=0.003
 Students should see how these numbers scale downwards as
the numbers shrink 10x in size for each transition
 Opposite of multiplying by 10
 Because when you multiply a decimal by a whole
you end up a part of a whole
 0.1x10=1
o 10 groups of 1 tenth (flat) = 1 whole (cube)
1
o 10x = 1
10
o Classic model (stacked)
 The pattern that will emerge through multiplication shows that the digits
move to appropriate positions

o Ex. Multiplying by 100 would force the digit in the ones place to move
 all other digits moving along with it
to the hundreds place, with
o Multiplying by 0.01 would force the digit in the ones place to move to
the hundredths place with all other numbers moving along with it
 White board work
o 1x5, 0.1x5, 0.01x5, 0.001x5
o 3x5, 0.3x5, 0.03x5, 0.003x5
o 5x5, 0.5x5, 0.05x5, 0.005x5
o 7x5, 0.7x5, 0.07x5, 0.007x5
Development:
 Connection to money
o 1.0= 1 dollar, 0.1=ten cents, 0.01=1 cent
o
 Move on to 1 digit by 2 digit decimal numbers
o 2.2x4
o One can of pop costs $2.20. How much will it cost for 4?
 How do we solve multiplication with decimals?
 Solve with the area model
 Estimate!
 2.2 rounds to 2, 2x4=8, so we know our answer is close
to 8.
 Next step is to multiply the decimal
 Use the area model as demonstrated previously
 2.2x4=8.8
 Other problems to solve with no regrouping
 3.3x2, 2.3x3, 4.2x2

Move on to 1 by 3 digit decimal numbers
o It takes 6.4m of fabric to create one Halloween costume. How much
fabric will it take to make 4 costumes?
 Work as a class and go through the steps
 Estimate and multiply, then solve
o It costs $0.35 for 1 big foot. How much will it cost for 8?
 Solve as a class
o Jackie walked 3.46km in 1 hour. How many kilometres could she walk
in 4 hours?
 Solve on their own
Expansion:
 Ask students to explain why dividing a number by 0.01 results in a greater
number than he/she originally started with
 Tell students that Jake said, “You always get a larger answer when you
multiply.” Ask them to respond to Jake's observation