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Finding the Fourth Proportional to 485.45, 728.18 and 138.79

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Solution

The fourth proportional to 485.45, 728.18 and 138.79 is: 208.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    485.45 : 728.18 = 138.79 : x
  2. Step 2: Convert to fraction form
    485.45/728.18 = 138.79/x
  3. Step 3: Cross multiply
    485.45x = 728.18 × 138.79
  4. Step 4: Simplify right side
    485.45x = 101,064.10
  5. Step 5: Solve for x
    x = 101,064.10/485.45
  6. Step 6: Final answer
    x = 208.19

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.