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Finding the Fourth Proportional to 103.90, 155 and 85.81

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Solution

The fourth proportional to 103.90, 155 and 85.81 is: 128.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    103.90 : 155 = 85.81 : x
  2. Step 2: Convert to fraction form
    103.90/155 = 85.81/x
  3. Step 3: Cross multiply
    103.90x = 155 × 85.81
  4. Step 4: Simplify right side
    103.90x = 13,300.55
  5. Step 5: Solve for x
    x = 13,300.55/103.90
  6. Step 6: Final answer
    x = 128.01

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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.