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Finding the Fourth Proportional to 1,391.80, 2,086.42 and 621.88

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Solution

The fourth proportional to 1,391.80, 2,086.42 and 621.88 is: 932.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.80 : 2,086.42 = 621.88 : x
  2. Step 2: Convert to fraction form
    1,391.80/2,086.42 = 621.88/x
  3. Step 3: Cross multiply
    1,391.80x = 2,086.42 × 621.88
  4. Step 4: Simplify right side
    1,391.80x = 1,297,502.87
  5. Step 5: Solve for x
    x = 1,297,502.87/1,391.80
  6. Step 6: Final answer
    x = 932.25

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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.