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Finding the Fourth Proportional to 128.51, 192.78 and 47.42

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Solution

The fourth proportional to 128.51, 192.78 and 47.42 is: 71.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.51 : 192.78 = 47.42 : x
  2. Step 2: Convert to fraction form
    128.51/192.78 = 47.42/x
  3. Step 3: Cross multiply
    128.51x = 192.78 × 47.42
  4. Step 4: Simplify right side
    128.51x = 9,140.66
  5. Step 5: Solve for x
    x = 9,140.66/128.51
  6. Step 6: Final answer
    x = 71.13

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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.