Friday, December 6, 2013

Late Math activity Thursday: 5.OA.A.1

I got busy the last couple of days and didn't get around to my post, but better late than never...
5.OA.A.1 states: Use parentheses, brackets, or braces in numerical expressions, and evaluate expressions with these symbols.

I felt that mathisfun.com explains the use of these well on this page.  Basically, each student should already know the order of operations (remember "Please excuse my dear Aunt Sally" ?).
  1. Parenthases
  2. Exponents
  3. Multiplication or Division  (working left to right)
  4. Addition or Subtraction  (working left to right)
As an activity for this CCSS I suggest making an equation and then throwing in some parentheses and then some parentheses and brackets.  Then talk about how the braces hold sets of numbers.

If you wanted you could have number cards to choose from and then fill in the blanks.
Here's my sample.

9 + 10 - 5 ÷ 7  x 4 = ?

With no parentheses you work left to right with any M or D you find...

9 + 10 - 5/7 x 4 = ?
9 + 10 - 20/7 =

then leave as fraction or find the decimal form.  2 6/7 or 2.857  I prefer fraction if it's not a nice decimal...

9 + 10 - 2 6/7 =

Then work left to right with A or S.

19 - 2 6/7 = 16 1/7 or 16.143

Now the same problem with some parentheses placed turns out differently.

9 + (10 - 5) ÷ 7  x 4 = ?

9 + 5 ÷ 7  x 4 = ?

9 + 5/7 x 4 =  9 + 20/7 = 9 + 2 6/7= 11 6/7

Now the same problem with parentheses and brackets turns out differently too.

[9 + (10 - 5)] ÷ 7  x 4 = ?

[9 + 5] ÷ 7  x 4 = ?

14 ÷ 7  x 4 = ?

2 x 4 = 8

How about one more parentheses?

[9 + (10 - 5)] ÷ (7  x 4) = ?

[ 9 + 5 ] ÷ 28 = ?

14 ÷ 28 = 14/28 = 1/2 or 0.5

It's kind of fun seeing the different answers just because of a parentheses or two and the math looks all complicated but it's actually quite easy : )

See you next week!  Have you done any math posts lately?


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