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Finding the Fourth Proportional to 85.42, 128.16 and 66.20

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Solution

The fourth proportional to 85.42, 128.16 and 66.20 is: 99.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.42 : 128.16 = 66.20 : x
  2. Step 2: Convert to fraction form
    85.42/128.16 = 66.20/x
  3. Step 3: Cross multiply
    85.42x = 128.16 × 66.20
  4. Step 4: Simplify right side
    85.42x = 8,483.55
  5. Step 5: Solve for x
    x = 8,483.55/85.42
  6. Step 6: Final answer
    x = 99.32

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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.