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Finding the Fourth Proportional to 428.88, 642.41 and 390.15

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Solution

The fourth proportional to 428.88, 642.41 and 390.15 is: 584.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.88 : 642.41 = 390.15 : x
  2. Step 2: Convert to fraction form
    428.88/642.41 = 390.15/x
  3. Step 3: Cross multiply
    428.88x = 642.41 × 390.15
  4. Step 4: Simplify right side
    428.88x = 250,636.26
  5. Step 5: Solve for x
    x = 250,636.26/428.88
  6. Step 6: Final answer
    x = 584.40

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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.