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Finding the Fourth Proportional to 660.99, 991.35 and 387.21

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Solution

The fourth proportional to 660.99, 991.35 and 387.21 is: 580.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    660.99 : 991.35 = 387.21 : x
  2. Step 2: Convert to fraction form
    660.99/991.35 = 387.21/x
  3. Step 3: Cross multiply
    660.99x = 991.35 × 387.21
  4. Step 4: Simplify right side
    660.99x = 383,860.63
  5. Step 5: Solve for x
    x = 383,860.63/660.99
  6. Step 6: Final answer
    x = 580.74

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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.