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Finding the Fourth Proportional to 85.76, 128.63 and 77.66

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Solution

The fourth proportional to 85.76, 128.63 and 77.66 is: 116.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.76 : 128.63 = 77.66 : x
  2. Step 2: Convert to fraction form
    85.76/128.63 = 77.66/x
  3. Step 3: Cross multiply
    85.76x = 128.63 × 77.66
  4. Step 4: Simplify right side
    85.76x = 9,988.96
  5. Step 5: Solve for x
    x = 9,988.96/85.76
  6. Step 6: Final answer
    x = 116.48

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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.