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Finding the Fourth Proportional to 421.40, 632.19 and 128.91

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Solution

The fourth proportional to 421.40, 632.19 and 128.91 is: 193.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.40 : 632.19 = 128.91 : x
  2. Step 2: Convert to fraction form
    421.40/632.19 = 128.91/x
  3. Step 3: Cross multiply
    421.40x = 632.19 × 128.91
  4. Step 4: Simplify right side
    421.40x = 81,495.61
  5. Step 5: Solve for x
    x = 81,495.61/421.40
  6. Step 6: Final answer
    x = 193.39

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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.