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Finding the Fourth Proportional to 420.39, 630.45 and 127.88

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Solution

The fourth proportional to 420.39, 630.45 and 127.88 is: 191.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.39 : 630.45 = 127.88 : x
  2. Step 2: Convert to fraction form
    420.39/630.45 = 127.88/x
  3. Step 3: Cross multiply
    420.39x = 630.45 × 127.88
  4. Step 4: Simplify right side
    420.39x = 80,621.16
  5. Step 5: Solve for x
    x = 80,621.16/420.39
  6. Step 6: Final answer
    x = 191.78

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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.