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Finding the Fourth Proportional to 1,221.53, 1,685.61 and 690.55

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Solution

The fourth proportional to 1,221.53, 1,685.61 and 690.55 is: 952.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.53 : 1,685.61 = 690.55 : x
  2. Step 2: Convert to fraction form
    1,221.53/1,685.61 = 690.55/x
  3. Step 3: Cross multiply
    1,221.53x = 1,685.61 × 690.55
  4. Step 4: Simplify right side
    1,221.53x = 1,163,989.56
  5. Step 5: Solve for x
    x = 1,163,989.56/1,221.53
  6. Step 6: Final answer
    x = 952.89

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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.