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Finding the Fourth Proportional to 421.17, 631.76 and 128.67

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Solution

The fourth proportional to 421.17, 631.76 and 128.67 is: 193.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.17 : 631.76 = 128.67 : x
  2. Step 2: Convert to fraction form
    421.17/631.76 = 128.67/x
  3. Step 3: Cross multiply
    421.17x = 631.76 × 128.67
  4. Step 4: Simplify right side
    421.17x = 81,287.92
  5. Step 5: Solve for x
    x = 81,287.92/421.17
  6. Step 6: Final answer
    x = 193.01

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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.