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Finding the Fourth Proportional to 89.20, 123.16 and 78.40

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Solution

The fourth proportional to 89.20, 123.16 and 78.40 is: 108.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    89.20 : 123.16 = 78.40 : x
  2. Step 2: Convert to fraction form
    89.20/123.16 = 78.40/x
  3. Step 3: Cross multiply
    89.20x = 123.16 × 78.40
  4. Step 4: Simplify right side
    89.20x = 9,655.74
  5. Step 5: Solve for x
    x = 9,655.74/89.20
  6. Step 6: Final answer
    x = 108.25

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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.