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Finding the Fourth Proportional to 123.98, 185.78 and 78.21

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Solution

The fourth proportional to 123.98, 185.78 and 78.21 is: 117.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    123.98 : 185.78 = 78.21 : x
  2. Step 2: Convert to fraction form
    123.98/185.78 = 78.21/x
  3. Step 3: Cross multiply
    123.98x = 185.78 × 78.21
  4. Step 4: Simplify right side
    123.98x = 14,530.05
  5. Step 5: Solve for x
    x = 14,530.05/123.98
  6. Step 6: Final answer
    x = 117.20

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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.