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Finding the Fourth Proportional to 86.88, 128.88 and 85.80

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Solution

The fourth proportional to 86.88, 128.88 and 85.80 is: 127.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.88 : 128.88 = 85.80 : x
  2. Step 2: Convert to fraction form
    86.88/128.88 = 85.80/x
  3. Step 3: Cross multiply
    86.88x = 128.88 × 85.80
  4. Step 4: Simplify right side
    86.88x = 11,057.90
  5. Step 5: Solve for x
    x = 11,057.90/86.88
  6. Step 6: Final answer
    x = 127.28

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Why These Related Problems?

These problems maintain the same ratio (1.48) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.