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Finding the Fourth Proportional to 86.84, 129.64 and 72.40

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Solution

The fourth proportional to 86.84, 129.64 and 72.40 is: 108.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.84 : 129.64 = 72.40 : x
  2. Step 2: Convert to fraction form
    86.84/129.64 = 72.40/x
  3. Step 3: Cross multiply
    86.84x = 129.64 × 72.40
  4. Step 4: Simplify right side
    86.84x = 9,385.94
  5. Step 5: Solve for x
    x = 9,385.94/86.84
  6. Step 6: Final answer
    x = 108.08

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.