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Finding the Fourth Proportional to 85.80, 129.30 and 80.40

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Solution

The fourth proportional to 85.80, 129.30 and 80.40 is: 121.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.80 : 129.30 = 80.40 : x
  2. Step 2: Convert to fraction form
    85.80/129.30 = 80.40/x
  3. Step 3: Cross multiply
    85.80x = 129.30 × 80.40
  4. Step 4: Simplify right side
    85.80x = 10,395.72
  5. Step 5: Solve for x
    x = 10,395.72/85.80
  6. Step 6: Final answer
    x = 121.16

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.