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Finding the Fourth Proportional to 1,218.74, 1,681.79 and 687.61

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Solution

The fourth proportional to 1,218.74, 1,681.79 and 687.61 is: 948.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,218.74 : 1,681.79 = 687.61 : x
  2. Step 2: Convert to fraction form
    1,218.74/1,681.79 = 687.61/x
  3. Step 3: Cross multiply
    1,218.74x = 1,681.79 × 687.61
  4. Step 4: Simplify right side
    1,218.74x = 1,156,407.98
  5. Step 5: Solve for x
    x = 1,156,407.98/1,218.74
  6. Step 6: Final answer
    x = 948.86

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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.