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Finding the Fourth Proportional to 76.40, 105.40 and 48.78

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Solution

The fourth proportional to 76.40, 105.40 and 48.78 is: 67.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.40 : 105.40 = 48.78 : x
  2. Step 2: Convert to fraction form
    76.40/105.40 = 48.78/x
  3. Step 3: Cross multiply
    76.40x = 105.40 × 48.78
  4. Step 4: Simplify right side
    76.40x = 5,141.41
  5. Step 5: Solve for x
    x = 5,141.41/76.40
  6. Step 6: Final answer
    x = 67.30

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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.