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Finding the Fourth Proportional to 1,115.65, 1,539.55 and 643.45

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Solution

The fourth proportional to 1,115.65, 1,539.55 and 643.45 is: 887.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,115.65 : 1,539.55 = 643.45 : x
  2. Step 2: Convert to fraction form
    1,115.65/1,539.55 = 643.45/x
  3. Step 3: Cross multiply
    1,115.65x = 1,539.55 × 643.45
  4. Step 4: Simplify right side
    1,115.65x = 990,623.45
  5. Step 5: Solve for x
    x = 990,623.45/1,115.65
  6. Step 6: Final answer
    x = 887.93

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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.