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Finding the Fourth Proportional to 1,221.10, 1,685.10 and 661.57

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Solution

The fourth proportional to 1,221.10, 1,685.10 and 661.57 is: 912.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.10 : 1,685.10 = 661.57 : x
  2. Step 2: Convert to fraction form
    1,221.10/1,685.10 = 661.57/x
  3. Step 3: Cross multiply
    1,221.10x = 1,685.10 × 661.57
  4. Step 4: Simplify right side
    1,221.10x = 1,114,799.87
  5. Step 5: Solve for x
    x = 1,114,799.87/1,221.10
  6. Step 6: Final answer
    x = 912.95

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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.