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Finding the Fourth Proportional to 420.85, 631.25 and 128.34

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Solution

The fourth proportional to 420.85, 631.25 and 128.34 is: 192.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.85 : 631.25 = 128.34 : x
  2. Step 2: Convert to fraction form
    420.85/631.25 = 128.34/x
  3. Step 3: Cross multiply
    420.85x = 631.25 × 128.34
  4. Step 4: Simplify right side
    420.85x = 81,014.63
  5. Step 5: Solve for x
    x = 81,014.63/420.85
  6. Step 6: Final answer
    x = 192.50

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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.