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Finding the Fourth Proportional to 128.40, 191.51 and 123.81

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Solution

The fourth proportional to 128.40, 191.51 and 123.81 is: 184.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.40 : 191.51 = 123.81 : x
  2. Step 2: Convert to fraction form
    128.40/191.51 = 123.81/x
  3. Step 3: Cross multiply
    128.40x = 191.51 × 123.81
  4. Step 4: Simplify right side
    128.40x = 23,710.23
  5. Step 5: Solve for x
    x = 23,710.23/128.40
  6. Step 6: Final answer
    x = 184.66

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.