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Finding the Fourth Proportional to 821.72, 1,131.36 and 780.68

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Solution

The fourth proportional to 821.72, 1,131.36 and 780.68 is: 1,074.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.72 : 1,131.36 = 780.68 : x
  2. Step 2: Convert to fraction form
    821.72/1,131.36 = 780.68/x
  3. Step 3: Cross multiply
    821.72x = 1,131.36 × 780.68
  4. Step 4: Simplify right side
    821.72x = 883,230.12
  5. Step 5: Solve for x
    x = 883,230.12/821.72
  6. Step 6: Final answer
    x = 1,074.86

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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.