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Finding the Fourth Proportional to 1,391.16, 2,086.71 and 660.21

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Solution

The fourth proportional to 1,391.16, 2,086.71 and 660.21 is: 990.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.16 : 2,086.71 = 660.21 : x
  2. Step 2: Convert to fraction form
    1,391.16/2,086.71 = 660.21/x
  3. Step 3: Cross multiply
    1,391.16x = 2,086.71 × 660.21
  4. Step 4: Simplify right side
    1,391.16x = 1,377,666.81
  5. Step 5: Solve for x
    x = 1,377,666.81/1,391.16
  6. Step 6: Final answer
    x = 990.30

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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.