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Finding the Fourth Proportional to 90.47, 135.90 and 78.72

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Solution

The fourth proportional to 90.47, 135.90 and 78.72 is: 118.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.47 : 135.90 = 78.72 : x
  2. Step 2: Convert to fraction form
    90.47/135.90 = 78.72/x
  3. Step 3: Cross multiply
    90.47x = 135.90 × 78.72
  4. Step 4: Simplify right side
    90.47x = 10,698.05
  5. Step 5: Solve for x
    x = 10,698.05/90.47
  6. Step 6: Final answer
    x = 118.26

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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.