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Finding the Fourth Proportional to 155, 213.85 and 99.78

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Solution

The fourth proportional to 155, 213.85 and 99.78 is: 137.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    155 : 213.85 = 99.78 : x
  2. Step 2: Convert to fraction form
    155/213.85 = 99.78/x
  3. Step 3: Cross multiply
    155x = 213.85 × 99.78
  4. Step 4: Simplify right side
    155x = 21,337.95
  5. Step 5: Solve for x
    x = 21,337.95/155
  6. Step 6: Final answer
    x = 137.66

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.