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Finding the Fourth Proportional to 85.66, 128.40 and 53.16

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Solution

The fourth proportional to 85.66, 128.40 and 53.16 is: 79.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.66 : 128.40 = 53.16 : x
  2. Step 2: Convert to fraction form
    85.66/128.40 = 53.16/x
  3. Step 3: Cross multiply
    85.66x = 128.40 × 53.16
  4. Step 4: Simplify right side
    85.66x = 6,825.74
  5. Step 5: Solve for x
    x = 6,825.74/85.66
  6. Step 6: Final answer
    x = 79.68

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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.