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Finding the Fourth Proportional to 86.16, 128.94 and 85.20

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Solution

The fourth proportional to 86.16, 128.94 and 85.20 is: 127.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.16 : 128.94 = 85.20 : x
  2. Step 2: Convert to fraction form
    86.16/128.94 = 85.20/x
  3. Step 3: Cross multiply
    86.16x = 128.94 × 85.20
  4. Step 4: Simplify right side
    86.16x = 10,985.69
  5. Step 5: Solve for x
    x = 10,985.69/86.16
  6. Step 6: Final answer
    x = 127.50

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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.