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Lesson 1: Letters and symbols in multiplication and division equations

# Unknowns with multiplication and division

Sal finds the missing number in multiplication and division equations. Created by Sal Khan.

## Want to join the conversation?

• What is an equation?
• In case you or anyone else on KA needs to know this, the word "equation" comes from the root "equal," so an "equation" is a math sentence, but it is a particular kind where the information on each side of the "equal" sign are equal to each other.
There are other kinds of math sentences called "inequalities" which you will learn more about later, where the information on either side of the inequality symbol (greater than, less than, etc.) are related to each other but are not equal.
• How do you now to find the missing number?
• All you have to do is move the variables to one place and the numbers to the other place. Like for an example.
5*_=25
Then, do this _
=25/5
__=5
It is division on the other side because once you move something to the opposite side, the sign changes. Did you get. I am sorry if you didn't
(1 vote)
• WAIT at why use the all those symbols and say like u and a and c instead of all that?
• The A,U,and C symbols are there to have you figure out the problom like. 1/c * 4/1 then you would have to figure out the problem. Hope that helps!
• how can you do negative numbers?Is it the same as regular numbers?\
• Kind of, but negative numbers are like so:-1 -2 -3.
Like regular but -50 is less than -1 I forgot how but it is. Hope this helps!:)
• Does all types division use decimals?
• No. But it depends what the question is asking you.
• this is so confusing it was teaching me aljibra
• It is okay, everybody has their challenges.
P.S. It is spelled Algebra... I think
• does that mean that this entire video is pre-algebra/algebra for 3rd graders?
• Algebra involves solving for unknowns using placeholders for those unknowns (we call those unknowns "variables"). In this video, he introduces the idea of these place holders with a blank (__), a ?, a smiley face, a star, an A, and B. This enables 3rd Graders to become familiar with these placeholders long before Algebra introduces them in more complicated calculations.
(1 vote)
• Is it possible to solve an equation with two unknowns and only one known?