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Finding the Fourth Proportional to 1,221.61, 1,685.80 and 742.90

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Solution

The fourth proportional to 1,221.61, 1,685.80 and 742.90 is: 1,025.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.61 : 1,685.80 = 742.90 : x
  2. Step 2: Convert to fraction form
    1,221.61/1,685.80 = 742.90/x
  3. Step 3: Cross multiply
    1,221.61x = 1,685.80 × 742.90
  4. Step 4: Simplify right side
    1,221.61x = 1,252,377.53
  5. Step 5: Solve for x
    x = 1,252,377.53/1,221.61
  6. Step 6: Final answer
    x = 1,025.19

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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.