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Finding the Fourth Proportional to 81.77, 122.40 and 64.40

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Solution

The fourth proportional to 81.77, 122.40 and 64.40 is: 96.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.77 : 122.40 = 64.40 : x
  2. Step 2: Convert to fraction form
    81.77/122.40 = 64.40/x
  3. Step 3: Cross multiply
    81.77x = 122.40 × 64.40
  4. Step 4: Simplify right side
    81.77x = 7,881.95
  5. Step 5: Solve for x
    x = 7,881.95/81.77
  6. Step 6: Final answer
    x = 96.40

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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.