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Finding the Fourth Proportional to 120.39, 165.99 and 78.99

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Solution

The fourth proportional to 120.39, 165.99 and 78.99 is: 108.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.39 : 165.99 = 78.99 : x
  2. Step 2: Convert to fraction form
    120.39/165.99 = 78.99/x
  3. Step 3: Cross multiply
    120.39x = 165.99 × 78.99
  4. Step 4: Simplify right side
    120.39x = 13,111.55
  5. Step 5: Solve for x
    x = 13,111.55/120.39
  6. Step 6: Final answer
    x = 108.91

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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.