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Finding the Fourth Proportional to 428.64, 639.86 and 398.64

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Solution

The fourth proportional to 428.64, 639.86 and 398.64 is: 595.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.64 : 639.86 = 398.64 : x
  2. Step 2: Convert to fraction form
    428.64/639.86 = 398.64/x
  3. Step 3: Cross multiply
    428.64x = 639.86 × 398.64
  4. Step 4: Simplify right side
    428.64x = 255,073.79
  5. Step 5: Solve for x
    x = 255,073.79/428.64
  6. Step 6: Final answer
    x = 595.08

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.