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Finding the Fourth Proportional to 89.40, 123.12 and 72.90

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Solution

The fourth proportional to 89.40, 123.12 and 72.90 is: 100.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    89.40 : 123.12 = 72.90 : x
  2. Step 2: Convert to fraction form
    89.40/123.12 = 72.90/x
  3. Step 3: Cross multiply
    89.40x = 123.12 × 72.90
  4. Step 4: Simplify right side
    89.40x = 8,975.45
  5. Step 5: Solve for x
    x = 8,975.45/89.40
  6. Step 6: Final answer
    x = 100.40

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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.