AAA Math
Aaa Math: Adding Two Digit Numbers
This lesson has an explanation for adding two-digit numbers using paper and pencil. There is also a game to practice your skills. The game gives you a percent score of your correct answers, as well as running totals of your correct and...
AAA Math
Aaa Math: Adding Two Digit Numbers Mentally
Read these two strategies for adding two-digit numbers in your head. Then try out the one you like better by playing the game. Running totals of your correct and incorrect answers as well as a percent score of your correct answers will...
National Council of Teachers of Mathematics
Nctm: Illuminations: Volt Meter
As you put the different type of batteries on the volt meter pay attention to the voltage equations in the table. See how positive and negative numbers interact.