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Finding the Fourth Proportional to 1,638.40, 2,455.40 and 856.78

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Solution

The fourth proportional to 1,638.40, 2,455.40 and 856.78 is: 1,284.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,638.40 : 2,455.40 = 856.78 : x
  2. Step 2: Convert to fraction form
    1,638.40/2,455.40 = 856.78/x
  3. Step 3: Cross multiply
    1,638.40x = 2,455.40 × 856.78
  4. Step 4: Simplify right side
    1,638.40x = 2,103,737.61
  5. Step 5: Solve for x
    x = 2,103,737.61/1,638.40
  6. Step 6: Final answer
    x = 1,284.02

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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.