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Finding the Fourth Proportional to 76.40, 105.20 and 61.84

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Solution

The fourth proportional to 76.40, 105.20 and 61.84 is: 85.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.40 : 105.20 = 61.84 : x
  2. Step 2: Convert to fraction form
    76.40/105.20 = 61.84/x
  3. Step 3: Cross multiply
    76.40x = 105.20 × 61.84
  4. Step 4: Simplify right side
    76.40x = 6,505.57
  5. Step 5: Solve for x
    x = 6,505.57/76.40
  6. Step 6: Final answer
    x = 85.15

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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.