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Finding the Fourth Proportional to 687.12, 1,030.40 and 445.20

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Solution

The fourth proportional to 687.12, 1,030.40 and 445.20 is: 667.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.12 : 1,030.40 = 445.20 : x
  2. Step 2: Convert to fraction form
    687.12/1,030.40 = 445.20/x
  3. Step 3: Cross multiply
    687.12x = 1,030.40 × 445.20
  4. Step 4: Simplify right side
    687.12x = 458,734.08
  5. Step 5: Solve for x
    x = 458,734.08/687.12
  6. Step 6: Final answer
    x = 667.62

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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.