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Finding the Fourth Proportional to 78.30, 108.18 and 66.15

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Solution

The fourth proportional to 78.30, 108.18 and 66.15 is: 91.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.30 : 108.18 = 66.15 : x
  2. Step 2: Convert to fraction form
    78.30/108.18 = 66.15/x
  3. Step 3: Cross multiply
    78.30x = 108.18 × 66.15
  4. Step 4: Simplify right side
    78.30x = 7,156.11
  5. Step 5: Solve for x
    x = 7,156.11/78.30
  6. Step 6: Final answer
    x = 91.39

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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.