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Finding the Fourth Proportional to 78.90, 108.72 and 63.42

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Solution

The fourth proportional to 78.90, 108.72 and 63.42 is: 87.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.90 : 108.72 = 63.42 : x
  2. Step 2: Convert to fraction form
    78.90/108.72 = 63.42/x
  3. Step 3: Cross multiply
    78.90x = 108.72 × 63.42
  4. Step 4: Simplify right side
    78.90x = 6,895.02
  5. Step 5: Solve for x
    x = 6,895.02/78.90
  6. Step 6: Final answer
    x = 87.39

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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.