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Finding the Fourth Proportional to 687.72, 1,025.79 and 642.36

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Solution

The fourth proportional to 687.72, 1,025.79 and 642.36 is: 958.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.72 : 1,025.79 = 642.36 : x
  2. Step 2: Convert to fraction form
    687.72/1,025.79 = 642.36/x
  3. Step 3: Cross multiply
    687.72x = 1,025.79 × 642.36
  4. Step 4: Simplify right side
    687.72x = 658,926.46
  5. Step 5: Solve for x
    x = 658,926.46/687.72
  6. Step 6: Final answer
    x = 958.13

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.