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Finding the Fourth Proportional to 1,381.40, 1,906.17 and 821.90

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Solution

The fourth proportional to 1,381.40, 1,906.17 and 821.90 is: 1,134.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,381.40 : 1,906.17 = 821.90 : x
  2. Step 2: Convert to fraction form
    1,381.40/1,906.17 = 821.90/x
  3. Step 3: Cross multiply
    1,381.40x = 1,906.17 × 821.90
  4. Step 4: Simplify right side
    1,381.40x = 1,566,681.12
  5. Step 5: Solve for x
    x = 1,566,681.12/1,381.40
  6. Step 6: Final answer
    x = 1,134.13

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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.