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Finding the Fourth Proportional to 78.09, 107.81 and 65.13

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Solution

The fourth proportional to 78.09, 107.81 and 65.13 is: 89.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.09 : 107.81 = 65.13 : x
  2. Step 2: Convert to fraction form
    78.09/107.81 = 65.13/x
  3. Step 3: Cross multiply
    78.09x = 107.81 × 65.13
  4. Step 4: Simplify right side
    78.09x = 7,021.34
  5. Step 5: Solve for x
    x = 7,021.34/78.09
  6. Step 6: Final answer
    x = 89.91

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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.