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Finding the Fourth Proportional to 100.65, 150.78 and 85.38

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Solution

The fourth proportional to 100.65, 150.78 and 85.38 is: 127.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.65 : 150.78 = 85.38 : x
  2. Step 2: Convert to fraction form
    100.65/150.78 = 85.38/x
  3. Step 3: Cross multiply
    100.65x = 150.78 × 85.38
  4. Step 4: Simplify right side
    100.65x = 12,873.60
  5. Step 5: Solve for x
    x = 12,873.60/100.65
  6. Step 6: Final answer
    x = 127.90

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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.