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Finding the Fourth Proportional to 90.40, 124.91 and 78.10

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Solution

The fourth proportional to 90.40, 124.91 and 78.10 is: 107.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.40 : 124.91 = 78.10 : x
  2. Step 2: Convert to fraction form
    90.40/124.91 = 78.10/x
  3. Step 3: Cross multiply
    90.40x = 124.91 × 78.10
  4. Step 4: Simplify right side
    90.40x = 9,755.35
  5. Step 5: Solve for x
    x = 9,755.35/90.40
  6. Step 6: Final answer
    x = 107.91

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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.