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Finding the Fourth Proportional to 1,286.48, 1,776.72 and 821

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Solution

The fourth proportional to 1,286.48, 1,776.72 and 821 is: 1,133.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,286.48 : 1,776.72 = 821 : x
  2. Step 2: Convert to fraction form
    1,286.48/1,776.72 = 821/x
  3. Step 3: Cross multiply
    1,286.48x = 1,776.72 × 821
  4. Step 4: Simplify right side
    1,286.48x = 1,458,687.12
  5. Step 5: Solve for x
    x = 1,458,687.12/1,286.48
  6. Step 6: Final answer
    x = 1,133.86

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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.