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Finding the Fourth Proportional to 1,121.64, 1,681.49 and 391.12

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Solution

The fourth proportional to 1,121.64, 1,681.49 and 391.12 is: 586.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.64 : 1,681.49 = 391.12 : x
  2. Step 2: Convert to fraction form
    1,121.64/1,681.49 = 391.12/x
  3. Step 3: Cross multiply
    1,121.64x = 1,681.49 × 391.12
  4. Step 4: Simplify right side
    1,121.64x = 657,655.96
  5. Step 5: Solve for x
    x = 657,655.96/1,121.64
  6. Step 6: Final answer
    x = 586.34

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.