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Finding the Fourth Proportional to 612, 918 and 420.84

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Solution

The fourth proportional to 612, 918 and 420.84 is: 631.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    612 : 918 = 420.84 : x
  2. Step 2: Convert to fraction form
    612/918 = 420.84/x
  3. Step 3: Cross multiply
    612x = 918 × 420.84
  4. Step 4: Simplify right side
    612x = 386,331.12
  5. Step 5: Solve for x
    x = 386,331.12/612
  6. Step 6: Final answer
    x = 631.26

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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.