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Finding the Fourth Proportional to 280, 420 and 128

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Solution

The fourth proportional to 280, 420 and 128 is: 192

Step by Step Solution

  1. Step 1: Write the proportion equation
    280 : 420 = 128 : x
  2. Step 2: Convert to fraction form
    280/420 = 128/x
  3. Step 3: Cross multiply
    280x = 420 × 128
  4. Step 4: Simplify right side
    280x = 53,760
  5. Step 5: Solve for x
    x = 53,760/280
  6. Step 6: Final answer
    x = 192

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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.