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Finding the Fourth Proportional to 1,221.76, 1,685.97 and 717.55

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Solution

The fourth proportional to 1,221.76, 1,685.97 and 717.55 is: 990.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.76 : 1,685.97 = 717.55 : x
  2. Step 2: Convert to fraction form
    1,221.76/1,685.97 = 717.55/x
  3. Step 3: Cross multiply
    1,221.76x = 1,685.97 × 717.55
  4. Step 4: Simplify right side
    1,221.76x = 1,209,763.56
  5. Step 5: Solve for x
    x = 1,209,763.56/1,221.76
  6. Step 6: Final answer
    x = 990.18

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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.