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### Unit 2: Lesson 1

Sal shows the relationship between 2+3=5, 5-2=3, and 5-3=2.

## Want to join the conversation?

• 2 green balls and 3 purple balls is 5 balls together
• that is correct mfunk0886. Good job for getting that correct.
• There are 4 types of basic adding, subtracting.( I think ). There is addition+, subtraction-,multiplicationX, and dividing/. Now, if you are willing to add, you need to take the first number and add that to the second number. Then you have your answer. Subtraction is different, I you have a number, and a different number than you have got to take away the how ever many numbers from the first number of the second number. Now, multiplication is a whole new level. The way you work this type is to add the first number however many times the second number is. Dividing is harder. You have the first number and the lower second number. You have got to put in the second number until you have the first. You count however many times you put in the second number until you have the remaining first number. Than you have the answer! Your welcome! (I hope this helps)
• Um what is a reciprocal
• Good question for first grade!

A reciprocal of a number is 1 divided by that number. Taking a reciprocal can also be thought of as switching the numerator (top) and denominator (bottom) of a fraction.

Examples:
Because 1 is 1/1, the reciprocal of 1 is just 1.
Since 3 is 3/1, the reciprocal of 3 is 1/3.
The reciprocal of 4/7 is 7/4, or 1 3/4.
Because 2 4/5 is 14/5, the reciprocal of 2 4/5 is 5/14.
0 is the only number without a reciprocal since 1/0 is undefined.

Note that any number (other than 0) times its reciprocal is always 1. Later on, when you study operations with fractions, you will learn that division by a number is the same as multiplication by that number's reciprocal.
• Just by looking at the addition problem we can also understand the subtraction problem without writing the subtraction problem.
• Math goes on infinitely, does that mean it goes infinitely both positively and negatively? So, if it is limitless in positive numbers (above zero), then would the opposite of infinity be 'negative infinity' or simply, again, infinity?
• 101010101001010101010100101
• i need help with my math. {PLZ HELP!}
• i ts easy 1,342+1,327=2,669