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Finding the Fourth Proportional to 687.12, 1,029.76 and 316.72

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Solution

The fourth proportional to 687.12, 1,029.76 and 316.72 is: 474.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.12 : 1,029.76 = 316.72 : x
  2. Step 2: Convert to fraction form
    687.12/1,029.76 = 316.72/x
  3. Step 3: Cross multiply
    687.12x = 1,029.76 × 316.72
  4. Step 4: Simplify right side
    687.12x = 326,138.85
  5. Step 5: Solve for x
    x = 326,138.85/687.12
  6. Step 6: Final answer
    x = 474.65

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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.