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Finding the Fourth Proportional to 90.90, 135.77 and 78.75

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Solution

The fourth proportional to 90.90, 135.77 and 78.75 is: 117.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.90 : 135.77 = 78.75 : x
  2. Step 2: Convert to fraction form
    90.90/135.77 = 78.75/x
  3. Step 3: Cross multiply
    90.90x = 135.77 × 78.75
  4. Step 4: Simplify right side
    90.90x = 10,692.57
  5. Step 5: Solve for x
    x = 10,692.57/90.90
  6. Step 6: Final answer
    x = 117.63

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.