2. Today’s Objectives...
We will review and discuss multiplying
decimals, including the HW: 91 and 79.
We will discuss and practice rounding
decimals, HW: 92 and 83.
3. Review:
Multiplying Decimals
Steps:
Ignore the decimal points and multiply as if the
numbers were whole numbers.
Count up the TOTAL number of decimal places, and
that’s how many are in your answer.
Add the decimal point to your answer.
Video:
http://www.mathplayground.com/howto_multiplyd
ecimals.html
Multiplying Decimals Online Game:
http://cemc2.math.uwaterloo.ca/mathfrog/english/kidz/decM
ulti6.shtml
5. Rounding Decimals
Activity: Rounding Practice
Rules for Rounding Decimals:
1. Find the place value you want (the "rounding digit") and
look at the digit just to the right of it.
2. If that digit is less than 5, do not change the rounding digit
but drop all digits to the right of it.
3. If that digit is greater than or equal to five, add one to the
rounding digit and drop all digits to the right of it.
http://www.math.com/school/subject1/lessons/S1U1L3GL.html
Example: Round 46.327 to the nearest hundredth.
More than 5, so the 2 becomes a 3.
46.327 --> 46.33
6. Rounding Decimals
Example:
Round 2.84 to the nearest tenth.
2.84 Less than 5, so the 8 stays the same.
--> 2.8
Round 2.84 to the nearest whole number.
2.8 More than 5, so the 2 becomes a 3..
--> 3
http://www.mathsisfun.com/rounding-numbers.html
7. Rounding Decimals
Round 2.84 to the nearest whole number
and 0.72 to the nearest tenth.
2.84is more than 5, so the 2 becomes a 3.
8 --> 3
2 is less than 5, so the 7 stays the same.
0.72 -->0.7
Multiply the rounded numbers:
3 x 0.7
