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Finding the Fourth Proportional to 1,392.56, 1,921.68 and 771.60

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Solution

The fourth proportional to 1,392.56, 1,921.68 and 771.60 is: 1,064.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,392.56 : 1,921.68 = 771.60 : x
  2. Step 2: Convert to fraction form
    1,392.56/1,921.68 = 771.60/x
  3. Step 3: Cross multiply
    1,392.56x = 1,921.68 × 771.60
  4. Step 4: Simplify right side
    1,392.56x = 1,482,768.29
  5. Step 5: Solve for x
    x = 1,482,768.29/1,392.56
  6. Step 6: Final answer
    x = 1,064.78

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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.