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Finding the Fourth Proportional to 21,915, 30,243.18 and 11,979

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Solution

The fourth proportional to 21,915, 30,243.18 and 11,979 is: 16,531.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    21,915 : 30,243.18 = 11,979 : x
  2. Step 2: Convert to fraction form
    21,915/30,243.18 = 11,979/x
  3. Step 3: Cross multiply
    21,915x = 30,243.18 × 11,979
  4. Step 4: Simplify right side
    21,915x = 362,283,053.22
  5. Step 5: Solve for x
    x = 362,283,053.22/21,915
  6. Step 6: Final answer
    x = 16,531.28

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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.