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Finding the Fourth Proportional to 1,115.72, 1,539.68 and 643.45

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Solution

The fourth proportional to 1,115.72, 1,539.68 and 643.45 is: 887.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,115.72 : 1,539.68 = 643.45 : x
  2. Step 2: Convert to fraction form
    1,115.72/1,539.68 = 643.45/x
  3. Step 3: Cross multiply
    1,115.72x = 1,539.68 × 643.45
  4. Step 4: Simplify right side
    1,115.72x = 990,707.10
  5. Step 5: Solve for x
    x = 990,707.10/1,115.72
  6. Step 6: Final answer
    x = 887.95

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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.