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Finding the Fourth Proportional to 90.72, 135.81 and 78.48

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Solution

The fourth proportional to 90.72, 135.81 and 78.48 is: 117.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.72 : 135.81 = 78.48 : x
  2. Step 2: Convert to fraction form
    90.72/135.81 = 78.48/x
  3. Step 3: Cross multiply
    90.72x = 135.81 × 78.48
  4. Step 4: Simplify right side
    90.72x = 10,658.37
  5. Step 5: Solve for x
    x = 10,658.37/90.72
  6. Step 6: Final answer
    x = 117.49

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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.