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Finding the Fourth Proportional to 921.61, 1,270.42 and 781.21

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Solution

The fourth proportional to 921.61, 1,270.42 and 781.21 is: 1,076.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.61 : 1,270.42 = 781.21 : x
  2. Step 2: Convert to fraction form
    921.61/1,270.42 = 781.21/x
  3. Step 3: Cross multiply
    921.61x = 1,270.42 × 781.21
  4. Step 4: Simplify right side
    921.61x = 992,464.81
  5. Step 5: Solve for x
    x = 992,464.81/921.61
  6. Step 6: Final answer
    x = 1,076.88

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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.