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Finding the Fourth Proportional to 1,428.32, 1,971.22 and 831

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Solution

The fourth proportional to 1,428.32, 1,971.22 and 831 is: 1,146.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,428.32 : 1,971.22 = 831 : x
  2. Step 2: Convert to fraction form
    1,428.32/1,971.22 = 831/x
  3. Step 3: Cross multiply
    1,428.32x = 1,971.22 × 831
  4. Step 4: Simplify right side
    1,428.32x = 1,638,083.82
  5. Step 5: Solve for x
    x = 1,638,083.82/1,428.32
  6. Step 6: Final answer
    x = 1,146.86

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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.