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Finding the Fourth Proportional to 86.21, 129.35 and 47.72

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Solution

The fourth proportional to 86.21, 129.35 and 47.72 is: 71.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.21 : 129.35 = 47.72 : x
  2. Step 2: Convert to fraction form
    86.21/129.35 = 47.72/x
  3. Step 3: Cross multiply
    86.21x = 129.35 × 47.72
  4. Step 4: Simplify right side
    86.21x = 6,172.05
  5. Step 5: Solve for x
    x = 6,172.05/86.21
  6. Step 6: Final answer
    x = 71.60

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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.