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Finding the Fourth Proportional to 1,290.74, 1,780.65 and 865.58

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Solution

The fourth proportional to 1,290.74, 1,780.65 and 865.58 is: 1,194.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.74 : 1,780.65 = 865.58 : x
  2. Step 2: Convert to fraction form
    1,290.74/1,780.65 = 865.58/x
  3. Step 3: Cross multiply
    1,290.74x = 1,780.65 × 865.58
  4. Step 4: Simplify right side
    1,290.74x = 1,541,286.12
  5. Step 5: Solve for x
    x = 1,541,286.12/1,290.74
  6. Step 6: Final answer
    x = 1,194.12

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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.