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Finding the Fourth Proportional to 72.40, 99.91 and 39.65

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Solution

The fourth proportional to 72.40, 99.91 and 39.65 is: 54.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    72.40 : 99.91 = 39.65 : x
  2. Step 2: Convert to fraction form
    72.40/99.91 = 39.65/x
  3. Step 3: Cross multiply
    72.40x = 99.91 × 39.65
  4. Step 4: Simplify right side
    72.40x = 3,961.23
  5. Step 5: Solve for x
    x = 3,961.23/72.40
  6. Step 6: Final answer
    x = 54.72

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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.