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Finding the Fourth Proportional to 102.78, 153.99 and 85.64

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Solution

The fourth proportional to 102.78, 153.99 and 85.64 is: 128.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.78 : 153.99 = 85.64 : x
  2. Step 2: Convert to fraction form
    102.78/153.99 = 85.64/x
  3. Step 3: Cross multiply
    102.78x = 153.99 × 85.64
  4. Step 4: Simplify right side
    102.78x = 13,186.93
  5. Step 5: Solve for x
    x = 13,186.93/102.78
  6. Step 6: Final answer
    x = 128.30

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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.