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Finding the Fourth Proportional to 86.16, 129.21 and 42.84

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Solution

The fourth proportional to 86.16, 129.21 and 42.84 is: 64.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.16 : 129.21 = 42.84 : x
  2. Step 2: Convert to fraction form
    86.16/129.21 = 42.84/x
  3. Step 3: Cross multiply
    86.16x = 129.21 × 42.84
  4. Step 4: Simplify right side
    86.16x = 5,535.36
  5. Step 5: Solve for x
    x = 5,535.36/86.16
  6. Step 6: Final answer
    x = 64.25

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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.