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Finding the Fourth Proportional to 76.80, 105.90 and 74.90

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Solution

The fourth proportional to 76.80, 105.90 and 74.90 is: 103.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.80 : 105.90 = 74.90 : x
  2. Step 2: Convert to fraction form
    76.80/105.90 = 74.90/x
  3. Step 3: Cross multiply
    76.80x = 105.90 × 74.90
  4. Step 4: Simplify right side
    76.80x = 7,931.91
  5. Step 5: Solve for x
    x = 7,931.91/76.80
  6. Step 6: Final answer
    x = 103.28

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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.