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Finding the Fourth Proportional to 86.72, 129.84 and 56.21

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Solution

The fourth proportional to 86.72, 129.84 and 56.21 is: 84.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.72 : 129.84 = 56.21 : x
  2. Step 2: Convert to fraction form
    86.72/129.84 = 56.21/x
  3. Step 3: Cross multiply
    86.72x = 129.84 × 56.21
  4. Step 4: Simplify right side
    86.72x = 7,298.31
  5. Step 5: Solve for x
    x = 7,298.31/86.72
  6. Step 6: Final answer
    x = 84.16

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.