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Finding the Fourth Proportional to 1,221.62, 1,686.22 and 780.71

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Solution

The fourth proportional to 1,221.62, 1,686.22 and 780.71 is: 1,077.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.62 : 1,686.22 = 780.71 : x
  2. Step 2: Convert to fraction form
    1,221.62/1,686.22 = 780.71/x
  3. Step 3: Cross multiply
    1,221.62x = 1,686.22 × 780.71
  4. Step 4: Simplify right side
    1,221.62x = 1,316,438.43
  5. Step 5: Solve for x
    x = 1,316,438.43/1,221.62
  6. Step 6: Final answer
    x = 1,077.62

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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.