Decimals and new Challenge Wednesday

Over the past two class periods we have been adding, subtracting, and multiplying decimals.  Here's the short version.  When you do any of these it is just the same as regular +, -, and x, but there are some basic decimal rules.

1. When adding or subtracting you always, ALWAYS, have to line up the decimals.  (Like a button down shirt, I stole that from Mr. Nelson)

2. When multiplying, we DO NOT line them up, but count them and then move it over in the answer.  Example:

23.4 x 3.2                        First, math books write it this way to save space, we want to do it vertically.

     23.4
  x   3.2                            That's better :) 
      468
 + 7020                           Multiply like normal ignoring the decimals.
    7488                           Life is good!  We have the answer with only the decimals left to deal with.
                                       We count how many numbers are after the decimals in the problem, top = 1,
                                       bottom number = 1, so two total.  Starting from the right, count two over and
                                       place the decimal.

     74.88                         That's it!

Huge congrats to Jazzmyn for solving the Challenge Problem #1.  Awesome Job!  A new video and problem are coming for Wednesday this week.  Enjoy! 

Here's the rundown of our Chapter, we're already at 3-4
3A UNDERSTANDING DECIMALS

• 3-1  Representing, Comparing & Ordering Decimals
• 3-2  Estimating Decimals
• 3-3  Adding and Subtraction Decimals

3B MULTIPLYING AND DIVIDING DECIMALS

• 3-4  Multiplying Decimals
• 3-5  Dividing Decimals by Whole Numbers
• 3-6  Dividing by Decimals
• 3-7  Interpreting the Quotient
• 3-8  Solving Decimal Equations