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Finding the Fourth Proportional to 2,145, 3,217.50 and 685.40

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Solution

The fourth proportional to 2,145, 3,217.50 and 685.40 is: 1,028.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,145 : 3,217.50 = 685.40 : x
  2. Step 2: Convert to fraction form
    2,145/3,217.50 = 685.40/x
  3. Step 3: Cross multiply
    2,145x = 3,217.50 × 685.40
  4. Step 4: Simplify right side
    2,145x = 2,205,274.50
  5. Step 5: Solve for x
    x = 2,205,274.50/2,145
  6. Step 6: Final answer
    x = 1,028.10

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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.