Simplify the Expression: Cube Root of √25 × Cube Root of √64

Radical Simplification with Nested Roots

Complete the following exercise:

253643= \sqrt[3]{\sqrt{25}}\cdot\sqrt[3]{\sqrt{64}}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve the following problem
00:05 A 'regular' root is of the order 2
00:08 Breakdown 25 to 5 squared
00:13 Breakdown 64 to 8 squared
00:17 The root of any number (A) squared cancels out the square
00:26 Apply this formula to our exercise and proceed to cancel out the squares
00:42 Breakdown 8 to 2 to the power of 3
00:50 A cube root cancels out a power of three
00:53 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Complete the following exercise:

253643= \sqrt[3]{\sqrt{25}}\cdot\sqrt[3]{\sqrt{64}}=

2

Step-by-step solution

To solve the problem 253643 \sqrt[3]{\sqrt{25}} \cdot \sqrt[3]{\sqrt{64}} , we will work through it step by step:

Step 1: Simplify the inner square roots.

  • 25\sqrt{25} simplifies to 55 because 5×5=255 \times 5 = 25.
  • 64\sqrt{64} simplifies to 88 because 8×8=648 \times 8 = 64.

Step 2: Evaluate the cube roots.

  • 53\sqrt[3]{5} remains as 51/35^{1/3}.
  • 83\sqrt[3]{8} evaluates to 22 because 2×2×2=82 \times 2 \times 2 = 8.

Step 3: Multiply the results of the cube roots.

  • 51/32=2535^{1/3} \cdot 2 = 2 \sqrt[3]{5}.

Thus, the simplified expression is 2532 \sqrt[3]{5}.

Therefore, the solution to the problem is 253 2\sqrt[3]{5} .

3

Final Answer

253 2\sqrt[3]{5}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Simplify innermost radicals before outer ones systematically
  • Technique: 25=5 \sqrt{25} = 5 and 64=8 \sqrt{64} = 8 , then evaluate cube roots
  • Check: Verify 23=8 2^3 = 8 and (253)3=40 (2\sqrt[3]{5})^3 = 40

Common Mistakes

Avoid these frequent errors
  • Trying to combine radicals before simplifying
    Don't multiply 253643 \sqrt[3]{\sqrt{25}} \cdot \sqrt[3]{\sqrt{64}} as 25643 \sqrt[3]{\sqrt{25 \cdot 64}} = wrong approach! This ignores the order of operations and creates messy calculations. Always simplify the innermost radicals first, then work outward step by step.

Practice Quiz

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Choose the largest value

FAQ

Everything you need to know about this question

Why can't I just multiply 25 and 64 inside the radicals?

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Because the radicals are nested! You have square roots inside cube roots, so you must follow the order of operations and simplify from the inside out. Multiplying 25 × 64 = 1600 first would give you a completely different problem.

How do I know when a cube root simplifies to a whole number?

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Look for perfect cubes! Numbers like 1, 8, 27, 64, 125 have cube roots that are whole numbers. Since 23=8 2^3 = 8 , we know 83=2 \sqrt[3]{8} = 2 .

What if the square root doesn't simplify nicely?

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If you get something like 50 \sqrt{50} , partially simplify it to 52 5\sqrt{2} first, then take the cube root. The process is the same - always simplify inner radicals before outer ones!

Can I use a calculator for this type of problem?

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While calculators help check your work, practice doing these by hand first! Recognizing perfect squares (25 = 5²) and perfect cubes (8 = 2³) builds your number sense and makes you faster at mental math.

Why is the final answer 253 2\sqrt[3]{5} and not just a decimal?

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Because 53 \sqrt[3]{5} is an irrational number that doesn't have a nice decimal form. Leaving it in radical form gives the exact answer, which is more precise than a rounded decimal approximation.

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