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Finding the Fourth Proportional to 1,115.40, 1,539.12 and 643.20

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Solution

The fourth proportional to 1,115.40, 1,539.12 and 643.20 is: 887.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,115.40 : 1,539.12 = 643.20 : x
  2. Step 2: Convert to fraction form
    1,115.40/1,539.12 = 643.20/x
  3. Step 3: Cross multiply
    1,115.40x = 1,539.12 × 643.20
  4. Step 4: Simplify right side
    1,115.40x = 989,961.98
  5. Step 5: Solve for x
    x = 989,961.98/1,115.40
  6. Step 6: Final answer
    x = 887.54

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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.