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Finding the Fourth Proportional to 85.76, 128 and 83.84

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Solution

The fourth proportional to 85.76, 128 and 83.84 is: 125.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.76 : 128 = 83.84 : x
  2. Step 2: Convert to fraction form
    85.76/128 = 83.84/x
  3. Step 3: Cross multiply
    85.76x = 128 × 83.84
  4. Step 4: Simplify right side
    85.76x = 10,731.52
  5. Step 5: Solve for x
    x = 10,731.52/85.76
  6. Step 6: Final answer
    x = 125.13

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.