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Finding the Fourth Proportional to 1,286.42, 1,929.64 and 420.74

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Solution

The fourth proportional to 1,286.42, 1,929.64 and 420.74 is: 631.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,286.42 : 1,929.64 = 420.74 : x
  2. Step 2: Convert to fraction form
    1,286.42/1,929.64 = 420.74/x
  3. Step 3: Cross multiply
    1,286.42x = 1,929.64 × 420.74
  4. Step 4: Simplify right side
    1,286.42x = 811,866.03
  5. Step 5: Solve for x
    x = 811,866.03/1,286.42
  6. Step 6: Final answer
    x = 631.10

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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.