Solve the Expression: 20-(1+9:9) Using Order of Operations

Order of Operations with Division Notation

20−(1+9:9)= 20-(1+9:9)=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:06 Let's solve this math problem together.
00:10 Remember, always start with the parentheses.
00:14 Next, do multiplication and division before addition and subtraction.
00:19 Calculate inside the parentheses first, then finish the rest of the expression.
00:25 And there you have the solution! Great job!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

20−(1+9:9)= 20-(1+9:9)=

2

Step-by-step solution

First, we solve the exercise in the parentheses

(1+9:9)= (1+9:9)=

According to the order of operations, we first divide and then add:

1+1=2 1+1=2

Now we obtain the exercise:

20−2=18 20-2=18

3

Final Answer

18 18

Key Points to Remember

Essential concepts to master this topic
  • Rule: Follow PEMDAS - solve parentheses first, then division inside
  • Technique: Calculate 9:9=1 9:9 = 1 , then 1+1=2 1+1 = 2
  • Check: Substitute back: 20−2=18 20-2 = 18 matches answer ✓

Common Mistakes

Avoid these frequent errors
  • Calculating left to right without following order
    Don't calculate 20-1 = 19 first then 19+9 = 28 then 28:9 = 3⅑! This ignores parentheses and order rules completely. Always solve what's in parentheses first using PEMDAS order.

Practice Quiz

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\( 100+5-100+5 \)

FAQ

Everything you need to know about this question

What does the colon symbol : mean in math?

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The colon symbol : means division, just like ÷. So 9:9 9:9 is the same as 9÷9=1 9 ÷ 9 = 1 .

Why do I solve the parentheses first?

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PEMDAS rules! Parentheses always come first, then you follow order of operations inside the parentheses. This ensures everyone gets the same answer.

What order do I follow inside the parentheses?

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Inside parentheses, follow PEMDAS: division comes before addition. So calculate 9:9=1 9:9 = 1 first, then 1+1=2 1+1 = 2 .

How can I remember the order of operations?

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Use PEMDAS: Please Excuse My Dear Aunt Sally

  • Parentheses
  • Exponents
  • Multiplication and Division (left to right)
  • Addition and Subtraction (left to right)

What if I got 20 as my answer?

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If you got 20, you likely forgot to do anything! Remember: you must solve the parentheses (1+9:9)=2 (1+9:9) = 2 first, then subtract from 20.

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