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Finding the Fourth Proportional to 1,392.12, 1,921.60 and 921.30

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Solution

The fourth proportional to 1,392.12, 1,921.60 and 921.30 is: 1,271.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,392.12 : 1,921.60 = 921.30 : x
  2. Step 2: Convert to fraction form
    1,392.12/1,921.60 = 921.30/x
  3. Step 3: Cross multiply
    1,392.12x = 1,921.60 × 921.30
  4. Step 4: Simplify right side
    1,392.12x = 1,770,370.08
  5. Step 5: Solve for x
    x = 1,770,370.08/1,392.12
  6. Step 6: Final answer
    x = 1,271.71

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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.