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Finding the Fourth Proportional to 72.55, 108.85 and 21.20

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Solution

The fourth proportional to 72.55, 108.85 and 21.20 is: 31.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    72.55 : 108.85 = 21.20 : x
  2. Step 2: Convert to fraction form
    72.55/108.85 = 21.20/x
  3. Step 3: Cross multiply
    72.55x = 108.85 × 21.20
  4. Step 4: Simplify right side
    72.55x = 2,307.72
  5. Step 5: Solve for x
    x = 2,307.72/72.55
  6. Step 6: Final answer
    x = 31.81

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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.