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Finding the Fourth Proportional to 420.77, 631.25 and 128.30

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Solution

The fourth proportional to 420.77, 631.25 and 128.30 is: 192.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.77 : 631.25 = 128.30 : x
  2. Step 2: Convert to fraction form
    420.77/631.25 = 128.30/x
  3. Step 3: Cross multiply
    420.77x = 631.25 × 128.30
  4. Step 4: Simplify right side
    420.77x = 80,986.47
  5. Step 5: Solve for x
    x = 80,986.47/420.77
  6. Step 6: Final answer
    x = 192.47

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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.