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### Course: 6th grade (Illustrative Mathematics)>Unit 6

Lesson 3: Lesson 3: Staying in balance

# Dividing both sides of an equation

In this lesson, we learn how to find the mass of a mystery object using a balanced scale. By keeping the scale balanced and taking equal portions from both sides, we can determine the mass of the mystery object. This helps us understand the concept of equality in real-life situations. Created by Sal Khan.

## Want to join the conversation?

• could you take 2x from both sides to find what x is?
• in an equation such as 1/2x=3+17 you could turn it into x=6+34 if that's what you mean
• why is a balance there
• to show how an equation works with the example of an old fashioned scale.
If you keep the scale balanced, the equation is correct, but if one side is heavier than the other side, you would not have a true equation.
• why didn't you do it the old fashion way 3x=9 and solve by doing in inverse opperation
• because he want us to learn the concept.
• At he says that 1/3 of this total mass is equal to 1/3 of that total mass. If the unknown mass was 5x and not 3x would you have to multiply by 1/5? Or if it was 8x would you have to multiply by 1/8?
• Yes, or instead you could divide by 5 or 8. In fact the division sign came from fractions...
• Cant you just count and see there are 9 kilograms on one side and divide the 9 by the number of mystery weights and get 3 ?
• the scale is drawn beautiful
• Well if you look closely you'll notice that the scales hanging thingies (don't know what you call them) aren't in line with the scale's stand so kind of trippie and looks like it's mid-swing(or maby it's better you don't look 'cuase you won't be able to unsee it).
• Is there a simpler way to do it?
• You can represent the equation mathematically as

3x = 9

and then divide both sides by 3 to get

x = 3.