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Finding the Fourth Proportional to 1,129.38, 1,692 and 781.72

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Solution

The fourth proportional to 1,129.38, 1,692 and 781.72 is: 1,171.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,129.38 : 1,692 = 781.72 : x
  2. Step 2: Convert to fraction form
    1,129.38/1,692 = 781.72/x
  3. Step 3: Cross multiply
    1,129.38x = 1,692 × 781.72
  4. Step 4: Simplify right side
    1,129.38x = 1,322,670.24
  5. Step 5: Solve for x
    x = 1,322,670.24/1,129.38
  6. Step 6: Final answer
    x = 1,171.15

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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.