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Finding the Fourth Proportional to 78, 107.40 and 61.57

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Solution

The fourth proportional to 78, 107.40 and 61.57 is: 84.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 107.40 = 61.57 : x
  2. Step 2: Convert to fraction form
    78/107.40 = 61.57/x
  3. Step 3: Cross multiply
    78x = 107.40 × 61.57
  4. Step 4: Simplify right side
    78x = 6,612.62
  5. Step 5: Solve for x
    x = 6,612.62/78
  6. Step 6: Final answer
    x = 84.78

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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.