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Finding the Fourth Proportional to 1,115.90, 1,539.90 and 643.73

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Solution

The fourth proportional to 1,115.90, 1,539.90 and 643.73 is: 888.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,115.90 : 1,539.90 = 643.73 : x
  2. Step 2: Convert to fraction form
    1,115.90/1,539.90 = 643.73/x
  3. Step 3: Cross multiply
    1,115.90x = 1,539.90 × 643.73
  4. Step 4: Simplify right side
    1,115.90x = 991,279.83
  5. Step 5: Solve for x
    x = 991,279.83/1,115.90
  6. Step 6: Final answer
    x = 888.32

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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.