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Finding the Fourth Proportional to 421.06, 631.56 and 128.56

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Solution

The fourth proportional to 421.06, 631.56 and 128.56 is: 192.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.06 : 631.56 = 128.56 : x
  2. Step 2: Convert to fraction form
    421.06/631.56 = 128.56/x
  3. Step 3: Cross multiply
    421.06x = 631.56 × 128.56
  4. Step 4: Simplify right side
    421.06x = 81,194.67
  5. Step 5: Solve for x
    x = 81,194.67/421.06
  6. Step 6: Final answer
    x = 192.83

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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.