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Finding the Fourth Proportional to 991.21, 1,485.43 and 579.78

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Solution

The fourth proportional to 991.21, 1,485.43 and 579.78 is: 868.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.21 : 1,485.43 = 579.78 : x
  2. Step 2: Convert to fraction form
    991.21/1,485.43 = 579.78/x
  3. Step 3: Cross multiply
    991.21x = 1,485.43 × 579.78
  4. Step 4: Simplify right side
    991.21x = 861,222.61
  5. Step 5: Solve for x
    x = 861,222.61/991.21
  6. Step 6: Final answer
    x = 868.86

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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.