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Finding the Fourth Proportional to 421.21, 631.65 and 128.62

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Solution

The fourth proportional to 421.21, 631.65 and 128.62 is: 192.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.21 : 631.65 = 128.62 : x
  2. Step 2: Convert to fraction form
    421.21/631.65 = 128.62/x
  3. Step 3: Cross multiply
    421.21x = 631.65 × 128.62
  4. Step 4: Simplify right side
    421.21x = 81,242.82
  5. Step 5: Solve for x
    x = 81,242.82/421.21
  6. Step 6: Final answer
    x = 192.88

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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.