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Finding the Fourth Proportional to 78, 107.70 and 61.71

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Solution

The fourth proportional to 78, 107.70 and 61.71 is: 85.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 107.70 = 61.71 : x
  2. Step 2: Convert to fraction form
    78/107.70 = 61.71/x
  3. Step 3: Cross multiply
    78x = 107.70 × 61.71
  4. Step 4: Simplify right side
    78x = 6,646.17
  5. Step 5: Solve for x
    x = 6,646.17/78
  6. Step 6: Final answer
    x = 85.21

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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.