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Finding the Fourth Proportional to 1,218.78, 1,681.65 and 721.17

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Solution

The fourth proportional to 1,218.78, 1,681.65 and 721.17 is: 995.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,218.78 : 1,681.65 = 721.17 : x
  2. Step 2: Convert to fraction form
    1,218.78/1,681.65 = 721.17/x
  3. Step 3: Cross multiply
    1,218.78x = 1,681.65 × 721.17
  4. Step 4: Simplify right side
    1,218.78x = 1,212,755.53
  5. Step 5: Solve for x
    x = 1,212,755.53/1,218.78
  6. Step 6: Final answer
    x = 995.06

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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.