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Finding the Fourth Proportional to 79.60, 109.68 and 72.40

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Solution

The fourth proportional to 79.60, 109.68 and 72.40 is: 99.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    79.60 : 109.68 = 72.40 : x
  2. Step 2: Convert to fraction form
    79.60/109.68 = 72.40/x
  3. Step 3: Cross multiply
    79.60x = 109.68 × 72.40
  4. Step 4: Simplify right side
    79.60x = 7,940.83
  5. Step 5: Solve for x
    x = 7,940.83/79.60
  6. Step 6: Final answer
    x = 99.76

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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.