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Finding the Fourth Proportional to 78.38, 117.56 and 66.20

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Solution

The fourth proportional to 78.38, 117.56 and 66.20 is: 99.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.38 : 117.56 = 66.20 : x
  2. Step 2: Convert to fraction form
    78.38/117.56 = 66.20/x
  3. Step 3: Cross multiply
    78.38x = 117.56 × 66.20
  4. Step 4: Simplify right side
    78.38x = 7,782.47
  5. Step 5: Solve for x
    x = 7,782.47/78.38
  6. Step 6: Final answer
    x = 99.29

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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.