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Finding the Fourth Proportional to 259.20, 388.70 and 85.76

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Solution

The fourth proportional to 259.20, 388.70 and 85.76 is: 128.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    259.20 : 388.70 = 85.76 : x
  2. Step 2: Convert to fraction form
    259.20/388.70 = 85.76/x
  3. Step 3: Cross multiply
    259.20x = 388.70 × 85.76
  4. Step 4: Simplify right side
    259.20x = 33,334.32
  5. Step 5: Solve for x
    x = 33,334.32/259.20
  6. Step 6: Final answer
    x = 128.60

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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.