Solve Mixed Number Expression: 2⅕ - (2⅕ - 1½)

Mixed Number Operations with Parentheses

215(215112)= 2\frac{1}{5}-(2\frac{1}{5}-1\frac{1}{2})=

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Step-by-step video solution

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00:00 Solve
00:03 When opening parentheses, minus times minus always equals plus
00:17 Let's solve according to the order of operations from left to right
00:22 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

215(215112)= 2\frac{1}{5}-(2\frac{1}{5}-1\frac{1}{2})=

2

Step-by-step solution

The given expression to evaluate is 215(215112) 2\frac{1}{5} - (2\frac{1}{5} - 1\frac{1}{2}) .

First, we perform the calculation inside the parentheses:

  • Convert 215 2\frac{1}{5} to an improper fraction: 215=115 2\frac{1}{5} = \frac{11}{5} .
  • Convert 112 1\frac{1}{2} to an improper fraction: 112=32 1\frac{1}{2} = \frac{3}{2} .

Now, perform the subtraction inside the parentheses:

(11532) \left( \frac{11}{5} - \frac{3}{2} \right)

To perform this subtraction, we need a common denominator. The least common denominator of 5 and 2 is 10.

  • Convert 115 \frac{11}{5} to 2210 \frac{22}{10} .
  • Convert 32 \frac{3}{2} to 1510 \frac{15}{10} .

Subtract the fractions:

22101510=710 \frac{22}{10} - \frac{15}{10} = \frac{7}{10} .

Now substitute this result back into the original expression:

215710 2\frac{1}{5} - \frac{7}{10} .

Again, convert 215 2\frac{1}{5} to 115=2210 \frac{11}{5} = \frac{22}{10} .

Now perform the subtraction:

2210710=1510 \frac{22}{10} - \frac{7}{10} = \frac{15}{10} .

Simplify the fraction 1510\frac{15}{10}:

1510=32 \frac{15}{10} = \frac{3}{2} .

Convert back to a mixed number if necessary, but here 32=112 \frac{3}{2} = 1\frac{1}{2} .

The solution to the problem is therefore: 112 1\frac{1}{2} .

3

Final Answer

112 1\frac{1}{2}

Key Points to Remember

Essential concepts to master this topic
  • Order of Operations: Always calculate inside parentheses first before outer operations
  • Technique: Convert to improper fractions: 215=115 2\frac{1}{5} = \frac{11}{5} , 112=32 1\frac{1}{2} = \frac{3}{2}
  • Check: Substitute back: 215(215112)=112 2\frac{1}{5} - (2\frac{1}{5} - 1\frac{1}{2}) = 1\frac{1}{2}

Common Mistakes

Avoid these frequent errors
  • Ignoring parentheses and calculating left to right
    Don't calculate 215215 2\frac{1}{5} - 2\frac{1}{5} first = wrong answer of 112 -1\frac{1}{2} ! This violates order of operations and changes the entire problem. Always solve what's inside parentheses first, then work outward.

Practice Quiz

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\( 100-(5+55)= \)

FAQ

Everything you need to know about this question

Why do I need to work inside the parentheses first?

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The order of operations (PEMDAS) requires parentheses first! If you ignore them, you're solving a completely different problem and will get the wrong answer.

Should I convert mixed numbers to improper fractions?

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Yes! Converting makes calculations much easier. 215=115 2\frac{1}{5} = \frac{11}{5} is simpler to work with than keeping it as a mixed number during operations.

How do I subtract fractions with different denominators?

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Find the least common denominator (LCD). For 5 and 2, the LCD is 10. Convert: 115=2210 \frac{11}{5} = \frac{22}{10} and 32=1510 \frac{3}{2} = \frac{15}{10} , then subtract.

What does the expression actually mean step by step?

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Think of it as: "Start with 215 2\frac{1}{5} , then subtract the result of (215112) (2\frac{1}{5} - 1\frac{1}{2}) ". The parentheses show what to calculate first.

Why is my answer different from the original numbers?

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That's normal! The expression 215(215112) 2\frac{1}{5} - (2\frac{1}{5} - 1\frac{1}{2}) simplifies to just 112 1\frac{1}{2} because of how the operations work together.

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