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Finding the Fourth Proportional to 421.17, 631.85 and 128.66

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Solution

The fourth proportional to 421.17, 631.85 and 128.66 is: 193.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.17 : 631.85 = 128.66 : x
  2. Step 2: Convert to fraction form
    421.17/631.85 = 128.66/x
  3. Step 3: Cross multiply
    421.17x = 631.85 × 128.66
  4. Step 4: Simplify right side
    421.17x = 81,296.07
  5. Step 5: Solve for x
    x = 81,296.07/421.17
  6. Step 6: Final answer
    x = 193.02

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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.