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Finding the Fourth Proportional to 2,145.79, 3,218.91 and 685

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Solution

The fourth proportional to 2,145.79, 3,218.91 and 685 is: 1,027.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,145.79 : 3,218.91 = 685 : x
  2. Step 2: Convert to fraction form
    2,145.79/3,218.91 = 685/x
  3. Step 3: Cross multiply
    2,145.79x = 3,218.91 × 685
  4. Step 4: Simplify right side
    2,145.79x = 2,204,953.35
  5. Step 5: Solve for x
    x = 2,204,953.35/2,145.79
  6. Step 6: Final answer
    x = 1,027.57

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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.