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Finding the Fourth Proportional to 78.36, 107.92 and 65.40

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Solution

The fourth proportional to 78.36, 107.92 and 65.40 is: 90.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.36 : 107.92 = 65.40 : x
  2. Step 2: Convert to fraction form
    78.36/107.92 = 65.40/x
  3. Step 3: Cross multiply
    78.36x = 107.92 × 65.40
  4. Step 4: Simplify right side
    78.36x = 7,057.97
  5. Step 5: Solve for x
    x = 7,057.97/78.36
  6. Step 6: Final answer
    x = 90.07

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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.