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Finding the Fourth Proportional to 498.40, 687.12 and 420.64

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Solution

The fourth proportional to 498.40, 687.12 and 420.64 is: 579.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    498.40 : 687.12 = 420.64 : x
  2. Step 2: Convert to fraction form
    498.40/687.12 = 420.64/x
  3. Step 3: Cross multiply
    498.40x = 687.12 × 420.64
  4. Step 4: Simplify right side
    498.40x = 289,030.16
  5. Step 5: Solve for x
    x = 289,030.16/498.40
  6. Step 6: Final answer
    x = 579.92

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.