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Finding the Fourth Proportional to 78.40, 108.15 and 47.30

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Solution

The fourth proportional to 78.40, 108.15 and 47.30 is: 65.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.40 : 108.15 = 47.30 : x
  2. Step 2: Convert to fraction form
    78.40/108.15 = 47.30/x
  3. Step 3: Cross multiply
    78.40x = 108.15 × 47.30
  4. Step 4: Simplify right side
    78.40x = 5,115.50
  5. Step 5: Solve for x
    x = 5,115.50/78.40
  6. Step 6: Final answer
    x = 65.25

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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.