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Finding the Fourth Proportional to 119.79, 165.30 and 78.40

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Solution

The fourth proportional to 119.79, 165.30 and 78.40 is: 108.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    119.79 : 165.30 = 78.40 : x
  2. Step 2: Convert to fraction form
    119.79/165.30 = 78.40/x
  3. Step 3: Cross multiply
    119.79x = 165.30 × 78.40
  4. Step 4: Simplify right side
    119.79x = 12,959.74
  5. Step 5: Solve for x
    x = 12,959.74/119.79
  6. Step 6: Final answer
    x = 108.19

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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.