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Finding the Fourth Proportional to 918.87, 1,378.34 and 431.58

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Solution

The fourth proportional to 918.87, 1,378.34 and 431.58 is: 647.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    918.87 : 1,378.34 = 431.58 : x
  2. Step 2: Convert to fraction form
    918.87/1,378.34 = 431.58/x
  3. Step 3: Cross multiply
    918.87x = 1,378.34 × 431.58
  4. Step 4: Simplify right side
    918.87x = 594,862.07
  5. Step 5: Solve for x
    x = 594,862.07/918.87
  6. Step 6: Final answer
    x = 647.39

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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.