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Finding the Fourth Proportional to 205.40, 307.89 and 128.42

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Solution

The fourth proportional to 205.40, 307.89 and 128.42 is: 192.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    205.40 : 307.89 = 128.42 : x
  2. Step 2: Convert to fraction form
    205.40/307.89 = 128.42/x
  3. Step 3: Cross multiply
    205.40x = 307.89 × 128.42
  4. Step 4: Simplify right side
    205.40x = 39,539.23
  5. Step 5: Solve for x
    x = 39,539.23/205.40
  6. Step 6: Final answer
    x = 192.50

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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.