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Finding the Fourth Proportional to 85.74, 128.43 and 56.87

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Solution

The fourth proportional to 85.74, 128.43 and 56.87 is: 85.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.74 : 128.43 = 56.87 : x
  2. Step 2: Convert to fraction form
    85.74/128.43 = 56.87/x
  3. Step 3: Cross multiply
    85.74x = 128.43 × 56.87
  4. Step 4: Simplify right side
    85.74x = 7,302.89
  5. Step 5: Solve for x
    x = 7,302.89/85.74
  6. Step 6: Final answer
    x = 85.17

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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.