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Finding the Fourth Proportional to 1,129.68, 1,690.68 and 642

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Solution

The fourth proportional to 1,129.68, 1,690.68 and 642 is: 960.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,129.68 : 1,690.68 = 642 : x
  2. Step 2: Convert to fraction form
    1,129.68/1,690.68 = 642/x
  3. Step 3: Cross multiply
    1,129.68x = 1,690.68 × 642
  4. Step 4: Simplify right side
    1,129.68x = 1,085,416.56
  5. Step 5: Solve for x
    x = 1,085,416.56/1,129.68
  6. Step 6: Final answer
    x = 960.82

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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.