Solve (√380.25 - ½)² - 11: Complete Square Root Expression

Order of Operations with Square Roots

(380.2512)211= (\sqrt{380.25}-\frac{1}{2})^2-11=

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Step-by-step video solution

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00:00 Solve the following problem
00:03 Calculate the root
00:12 Always calculate the parentheses first
00:19 Calculate the exponent
00:24 This is the solution

Step-by-step written solution

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1

Understand the problem

(380.2512)211= (\sqrt{380.25}-\frac{1}{2})^2-11=

2

Step-by-step solution

According to the order of operations, we should first solve the expression inside of the parentheses:

(380.2512)=(19.512)=(19) (\sqrt{380.25}-\frac{1}{2})=(19.5-\frac{1}{2})=(19)

In the next step, we will proceed to solve the exponentiation, and finally the subtraction:

(19)211=(19×19)11=36111=350 (19)^2-11=(19\times19)-11=361-11=350

3

Final Answer

350

Key Points to Remember

Essential concepts to master this topic
  • Parentheses First: Calculate inside parentheses before applying exponents or other operations
  • Square Root Technique: 380.25=19.5 \sqrt{380.25} = 19.5 since 19.52=380.25 19.5^2 = 380.25
  • Verification: Check final answer by working backwards: 350 + 11 = 361 = 19² ✓

Common Mistakes

Avoid these frequent errors
  • Squaring the entire expression before simplifying inside parentheses
    Don't square (380.2512)2 (\sqrt{380.25}-\frac{1}{2})^2 as 380.2514 380.25 - \frac{1}{4} = wrong expansion! This skips the parentheses rule and gives incorrect results. Always simplify inside parentheses first: 380.2512=19.50.5=19 \sqrt{380.25} - \frac{1}{2} = 19.5 - 0.5 = 19 , then square to get 361.

Practice Quiz

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\( \sqrt{100}= \)

FAQ

Everything you need to know about this question

How do I find the square root of 380.25?

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Since 380.25 is a decimal, look for a decimal that when squared gives 380.25. Try 19.5: 19.5×19.5=380.25 19.5 \times 19.5 = 380.25 . You can also recognize that 380.25=15214 380.25 = \frac{1521}{4} and 15214=392=19.5 \sqrt{\frac{1521}{4}} = \frac{39}{2} = 19.5 .

Why can't I just distribute the square over the subtraction?

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Because squaring doesn't distribute! (ab)2a2b2 (a-b)^2 \neq a^2 - b^2 . Instead, (ab)2=a22ab+b2 (a-b)^2 = a^2 - 2ab + b^2 . It's much easier to simplify inside the parentheses first, then square the result.

What if I get 19 - 0.5 = 18.5 instead of 19?

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Check your fraction conversion! 12=0.5 \frac{1}{2} = 0.5 , so 19.50.5=19 19.5 - 0.5 = 19 exactly. If you wrote 19.5 - 0.5 = 18.5, you made an arithmetic error in decimal subtraction.

How do I remember the order of operations with parentheses and exponents?

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Use PEMDAS (Parentheses, Exponents, Multiplication/Division, Addition/Subtraction). Always work from inside parentheses outward, then handle exponents, then other operations left to right.

Can I check my work without doing the whole problem again?

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Yes! Work backwards: if your answer is 350, then 350 + 11 = 361. Check if 361=19 \sqrt{361} = 19 , and if 19 + 0.5 = 19.5, and if 19.52=380.25 19.5^2 = 380.25 . This confirms your answer!

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