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Finding the Fourth Proportional to 719.20, 992.40 and 420.40

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Solution

The fourth proportional to 719.20, 992.40 and 420.40 is: 580.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    719.20 : 992.40 = 420.40 : x
  2. Step 2: Convert to fraction form
    719.20/992.40 = 420.40/x
  3. Step 3: Cross multiply
    719.20x = 992.40 × 420.40
  4. Step 4: Simplify right side
    719.20x = 417,204.96
  5. Step 5: Solve for x
    x = 417,204.96/719.20
  6. Step 6: Final answer
    x = 580.10

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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.