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Finding the Fourth Proportional to 57.21, 85.80 and 21.15

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Solution

The fourth proportional to 57.21, 85.80 and 21.15 is: 31.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    57.21 : 85.80 = 21.15 : x
  2. Step 2: Convert to fraction form
    57.21/85.80 = 21.15/x
  3. Step 3: Cross multiply
    57.21x = 85.80 × 21.15
  4. Step 4: Simplify right side
    57.21x = 1,814.67
  5. Step 5: Solve for x
    x = 1,814.67/57.21
  6. Step 6: Final answer
    x = 31.72

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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.