Hope you are enjoying the long weekend with your family.

Math
On Friday we practiced several mental math strategies. Everyone should be able to calculate two-digit by two-digit addition and subtraction MENTALLY. That means not using a pencil and paper or a calculator.

Addition
Making magic tens or friendly numbers:
Look for pairs of numbers in the ones place that add to make ten.
Example:
36 + 24 = 30 + 20 + 10 = 60

Adding in chunks:
Decompose one number (usually the smaller addend) and add in steps or chunks.
Example:
46 + 38 = 46 + 30 = 76 + 8 = 84

Place value:
Add the tens then add the ones. This strategy is a bit like adding in chunks because we are decomposing the addends.
Example:
78 + 19 = 70 + 8 + 10 + 9 = 80 + 17 = 97

Compensation (give and take):
Add a number to one of the addends to make a magic ten or friendly number then subtract the same amount from that number. When both addends are near a magic ten, I tend to make the larger addend the magic ten.
Example:
28 (-3) + 37 (+3)= 25 + 40 = 65

Doubles or near doubles:
This strategy works when both the addends are close to a magic ten. Be careful. If you added one to each addend, you must subtract 2 to the get the final answer.
Example:
39 + 39 = 40 + 40 -2 = 78

Subtraction:
Counting back:
This strategy works when the subtrahend is a single digit number. Think of the related subtract fact.
Example:
55 - 8 = 47 because 15 - 8= 7 so the answer has a 7 in the ones place and one less ten

Making an easier question:
When we use this strategy we are shifting the difference. You can either add the same amount to the minuend and subtrahend or take away the same amount. In each case you are trying to end up with a new subtraction question with no regrouping.
Example:
80 (-1) - 57 (-1) = 79 - 56 = 23

Subtracting in chunks:
Just like with addition, we decompose the subtrahend and take a bit away at a time.
Example:
61 - 47 = 61 - 40 = 21 - 1 = 20 - 6 = 14
In the question above we decomposed 47 into 40 + 6 + 1

Adding up:
We know that subtraction and addition are opposite so we can think of the related addition question with an unknown addend.
Example:
63 - 39 = 39 + ___ = 63
39 + 1 = 40
40 + 20 = 60
60 + 3 = 63

1 + 20 + 3 = 24

Of course you can use any combination of these strategies and apply them when adding or subtracting larger numbers.

Some practice:

Here's are a few puzzles for you to solve.....

Here is one possible solution. You may only use a digit once.

Science

Look around the house for examples of heat, light, electrical, sound, mechanical and chemical energies at home if you haven't already done so. Write them on the chart at the front of the room.

Remember....

Reminders:

• Tubing permission forms (Thursday)
• Dance-a-thon pledge forms (Wednesday)