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Finding the Fourth Proportional to 81.21, 111.99 and 56.30

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Solution

The fourth proportional to 81.21, 111.99 and 56.30 is: 77.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.21 : 111.99 = 56.30 : x
  2. Step 2: Convert to fraction form
    81.21/111.99 = 56.30/x
  3. Step 3: Cross multiply
    81.21x = 111.99 × 56.30
  4. Step 4: Simplify right side
    81.21x = 6,305.04
  5. Step 5: Solve for x
    x = 6,305.04/81.21
  6. Step 6: Final answer
    x = 77.64

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.