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Finding the Fourth Proportional to 1,115.80, 1,539.80 and 643.70

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Solution

The fourth proportional to 1,115.80, 1,539.80 and 643.70 is: 888.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,115.80 : 1,539.80 = 643.70 : x
  2. Step 2: Convert to fraction form
    1,115.80/1,539.80 = 643.70/x
  3. Step 3: Cross multiply
    1,115.80x = 1,539.80 × 643.70
  4. Step 4: Simplify right side
    1,115.80x = 991,169.26
  5. Step 5: Solve for x
    x = 991,169.26/1,115.80
  6. Step 6: Final answer
    x = 888.30

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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.