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Finding the Fourth Proportional to 78, 107.46 and 64.20

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Solution

The fourth proportional to 78, 107.46 and 64.20 is: 88.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 107.46 = 64.20 : x
  2. Step 2: Convert to fraction form
    78/107.46 = 64.20/x
  3. Step 3: Cross multiply
    78x = 107.46 × 64.20
  4. Step 4: Simplify right side
    78x = 6,898.93
  5. Step 5: Solve for x
    x = 6,898.93/78
  6. Step 6: Final answer
    x = 88.45

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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.