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Finding the Fourth Proportional to 420.74, 631.21 and 128.23

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Solution

The fourth proportional to 420.74, 631.21 and 128.23 is: 192.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.74 : 631.21 = 128.23 : x
  2. Step 2: Convert to fraction form
    420.74/631.21 = 128.23/x
  3. Step 3: Cross multiply
    420.74x = 631.21 × 128.23
  4. Step 4: Simplify right side
    420.74x = 80,940.06
  5. Step 5: Solve for x
    x = 80,940.06/420.74
  6. Step 6: Final answer
    x = 192.38

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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.