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Finding the Fourth Proportional to 420.10, 629.90 and 257.90

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Solution

The fourth proportional to 420.10, 629.90 and 257.90 is: 386.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.10 : 629.90 = 257.90 : x
  2. Step 2: Convert to fraction form
    420.10/629.90 = 257.90/x
  3. Step 3: Cross multiply
    420.10x = 629.90 × 257.90
  4. Step 4: Simplify right side
    420.10x = 162,451.21
  5. Step 5: Solve for x
    x = 162,451.21/420.10
  6. Step 6: Final answer
    x = 386.70

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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.