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Finding the Fourth Proportional to 78.21, 117.39 and 42.17

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Solution

The fourth proportional to 78.21, 117.39 and 42.17 is: 63.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.21 : 117.39 = 42.17 : x
  2. Step 2: Convert to fraction form
    78.21/117.39 = 42.17/x
  3. Step 3: Cross multiply
    78.21x = 117.39 × 42.17
  4. Step 4: Simplify right side
    78.21x = 4,949.75
  5. Step 5: Solve for x
    x = 4,949.75/78.21
  6. Step 6: Final answer
    x = 63.29

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.