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Finding the Fourth Proportional to 86.16, 128.88 and 85.08

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Solution

The fourth proportional to 86.16, 128.88 and 85.08 is: 127.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.16 : 128.88 = 85.08 : x
  2. Step 2: Convert to fraction form
    86.16/128.88 = 85.08/x
  3. Step 3: Cross multiply
    86.16x = 128.88 × 85.08
  4. Step 4: Simplify right side
    86.16x = 10,965.11
  5. Step 5: Solve for x
    x = 10,965.11/86.16
  6. Step 6: Final answer
    x = 127.26

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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.