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Finding the Fourth Proportional to 1,285.70, 1,928.57 and 420

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Solution

The fourth proportional to 1,285.70, 1,928.57 and 420 is: 630.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,285.70 : 1,928.57 = 420 : x
  2. Step 2: Convert to fraction form
    1,285.70/1,928.57 = 420/x
  3. Step 3: Cross multiply
    1,285.70x = 1,928.57 × 420
  4. Step 4: Simplify right side
    1,285.70x = 809,997.30
  5. Step 5: Solve for x
    x = 809,997.30/1,285.70
  6. Step 6: Final answer
    x = 630.01

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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.