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Finding the Fourth Proportional to 99.78, 149.31 and 86.99

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Solution

The fourth proportional to 99.78, 149.31 and 86.99 is: 130.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.78 : 149.31 = 86.99 : x
  2. Step 2: Convert to fraction form
    99.78/149.31 = 86.99/x
  3. Step 3: Cross multiply
    99.78x = 149.31 × 86.99
  4. Step 4: Simplify right side
    99.78x = 12,987.73
  5. Step 5: Solve for x
    x = 12,987.73/99.78
  6. Step 6: Final answer
    x = 130.16

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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.