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Finding the Fourth Proportional to 989.31, 1,365.21 and 639.99

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Solution

The fourth proportional to 989.31, 1,365.21 and 639.99 is: 883.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    989.31 : 1,365.21 = 639.99 : x
  2. Step 2: Convert to fraction form
    989.31/1,365.21 = 639.99/x
  3. Step 3: Cross multiply
    989.31x = 1,365.21 × 639.99
  4. Step 4: Simplify right side
    989.31x = 873,720.75
  5. Step 5: Solve for x
    x = 873,720.75/989.31
  6. Step 6: Final answer
    x = 883.16

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.