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Finding the Fourth Proportional to 78.28, 108.16 and 65.90

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Solution

The fourth proportional to 78.28, 108.16 and 65.90 is: 91.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.28 : 108.16 = 65.90 : x
  2. Step 2: Convert to fraction form
    78.28/108.16 = 65.90/x
  3. Step 3: Cross multiply
    78.28x = 108.16 × 65.90
  4. Step 4: Simplify right side
    78.28x = 7,127.74
  5. Step 5: Solve for x
    x = 7,127.74/78.28
  6. Step 6: Final answer
    x = 91.05

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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.