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### Course: Class 7 (Foundation)>Unit 1

Lesson 3: Using brackets

# Evaluating expressions with & without parentheses

Explore the concept of order of operations, emphasizing the importance of parentheses in mathematical expressions.Learn how the placement of parentheses can drastically change the outcome of an expression, highlighting the need to follow the correct sequence: parentheses, multiplication and division, then addition and subtraction. Created by Sal Khan.

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• What's the difference between parentheses(), curly brackets{}, and brackets[]?
• Parentheses () are used to group numbers or expressions that you want to calculate first. For example, in 2 + (3 × 4), you do 3 × 4 first because it is inside the parentheses.
Curly brackets {} are used to show sets of numbers or objects. A set is a collection of things that have something in common. For example, {1, 2, 3} is a set of three numbers.
Brackets [] are basically only used when you have more than one pair of parentheses in an expression. You use them outside the parentheses to show what to do next. For example, in [2 + (3 × 4)] ÷ 5 , you do 2 + (3 × 4) first because it is inside the brackets.

In a complicated expression, all three can be used, in this order: parentheses first, then brackets, then curly brackets. For example:

4 - 3 [4 - 2 {6 - (5 + 1)}] ÷ 3
First: 4 -3 [4 -2 {6 - 6}] ÷ 3
Then: 4 -3 [4 -2 × 0] ÷ 3
Then: 4 - 3 × 4 ÷ 3
Then: -8 ÷ 3
So the answer is -8 divided by 3.
• why does the math seem easier in the videos than in reality
• Because the people who makes the videos know how to do math really good.
• can you please show more examples because those two were helpful and i did understand it but it is still pretty confusing
• Hi 26noelbrooklyn

So another example that parentheses can change things is when you solve (8-3)x2 and 8-3x2.
So, let's solve the first one. According to the order of operations, we have to do parentheses first. 8-3 is 5. Then we do the multiplication. 5 times 2 is 10 so the answer to the first problem is 10.
Now let's solve the next one. Since there are no parentheses we solve the multiplication fist. 3 times 2 is 6. Then we do the subtraction. 8-6 is 2 so our answer is 2.
In conclusion your answers can be different based on parentheses. I hope this helps!
• Doesn't a negative plus a negative equal a positive number.
• A negative plus a negative will always equal a negative because you are taking a value less than zero and "applying more negativity to it" For example, you are already underground, and adding a negative distance means you will be digging even deeper underground.
However, a negative times a negative will become positive.
• what if there is two perethisis and that's what I don't get and what I mean is witch one should I do first if you know lease explain it to me thanks so much!
• In the example equation:
(10 × 4) + (4 ÷ 2)
You must solve the parenthesis first (Moving left to right)
(10 × 4 = 40) + (4 ÷ 2)
40 + (4 ÷ 2 = 2)
40 + 2 = 42

In this other example parentheses inside of parentheses:
((10 × (4 ÷ 2)) × 2) + 2
You solve the most nested parentheses first.
((10 × (4 ÷ 2 = 2)) × 2) + 2
((10 × 2 = 20) × 2) + 2
(20 × 2 = 40) + 2
40 + 2 = 42

Did this help? If so, great! If not, explain to me what you still don't understand.
• 1-(4-2x12)+7 in that problem,inside the parentheses, do i do the multiplication first, or the subtraction?
• you do the multiplication, because you have to do PEMDAS
• I have a Quick Questions how bo you do that
• Isn't this basically Bidmas??
• Yes, that's exactly what it is. You follow order of operations rules.
• At , i really dont get it
• At this point in the video, Sal is adding/subtracting Follow the rules for working with signed numbers. Work left to right.
8-24 = -16
-16-3 = -19
Hope this helps.
• For a company picnic, Todd fills 30 paper cups with ketchup and Yuki fills 27 paper cups with ketchup. Each paper cup holds 1 ounce. Later, Todd and Yuki learn that two other company employees completed exactly the same task.

Question 1
Part A

Write a numerical expression to find how many ounces of ketchup the four employees prepared.

Enter the correct answer in the box.