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Finding the Fourth Proportional to 78.40, 116.78 and 74.89

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Solution

The fourth proportional to 78.40, 116.78 and 74.89 is: 111.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.40 : 116.78 = 74.89 : x
  2. Step 2: Convert to fraction form
    78.40/116.78 = 74.89/x
  3. Step 3: Cross multiply
    78.40x = 116.78 × 74.89
  4. Step 4: Simplify right side
    78.40x = 8,745.65
  5. Step 5: Solve for x
    x = 8,745.65/78.40
  6. Step 6: Final answer
    x = 111.55

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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.