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Finding the Fourth Proportional to 90.20, 124.80 and 78.72

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Solution

The fourth proportional to 90.20, 124.80 and 78.72 is: 108.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.20 : 124.80 = 78.72 : x
  2. Step 2: Convert to fraction form
    90.20/124.80 = 78.72/x
  3. Step 3: Cross multiply
    90.20x = 124.80 × 78.72
  4. Step 4: Simplify right side
    90.20x = 9,824.26
  5. Step 5: Solve for x
    x = 9,824.26/90.20
  6. Step 6: Final answer
    x = 108.92

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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.