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Finding the Fourth Proportional to 1,286.80, 1,930.40 and 420.84

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Solution

The fourth proportional to 1,286.80, 1,930.40 and 420.84 is: 631.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,286.80 : 1,930.40 = 420.84 : x
  2. Step 2: Convert to fraction form
    1,286.80/1,930.40 = 420.84/x
  3. Step 3: Cross multiply
    1,286.80x = 1,930.40 × 420.84
  4. Step 4: Simplify right side
    1,286.80x = 812,389.54
  5. Step 5: Solve for x
    x = 812,389.54/1,286.80
  6. Step 6: Final answer
    x = 631.33

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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.