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Finding the Fourth Proportional to 76.89, 105.78 and 71.39

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Solution

The fourth proportional to 76.89, 105.78 and 71.39 is: 98.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.89 : 105.78 = 71.39 : x
  2. Step 2: Convert to fraction form
    76.89/105.78 = 71.39/x
  3. Step 3: Cross multiply
    76.89x = 105.78 × 71.39
  4. Step 4: Simplify right side
    76.89x = 7,551.11
  5. Step 5: Solve for x
    x = 7,551.11/76.89
  6. Step 6: Final answer
    x = 98.21

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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.