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Finding the Fourth Proportional to 1,391.40, 2,087.64 and 417.78

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Solution

The fourth proportional to 1,391.40, 2,087.64 and 417.78 is: 626.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.40 : 2,087.64 = 417.78 : x
  2. Step 2: Convert to fraction form
    1,391.40/2,087.64 = 417.78/x
  3. Step 3: Cross multiply
    1,391.40x = 2,087.64 × 417.78
  4. Step 4: Simplify right side
    1,391.40x = 872,174.24
  5. Step 5: Solve for x
    x = 872,174.24/1,391.40
  6. Step 6: Final answer
    x = 626.83

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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.