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Finding the Fourth Proportional to 85.65, 128.37 and 31.50

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Solution

The fourth proportional to 85.65, 128.37 and 31.50 is: 47.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.65 : 128.37 = 31.50 : x
  2. Step 2: Convert to fraction form
    85.65/128.37 = 31.50/x
  3. Step 3: Cross multiply
    85.65x = 128.37 × 31.50
  4. Step 4: Simplify right side
    85.65x = 4,043.77
  5. Step 5: Solve for x
    x = 4,043.77/85.65
  6. Step 6: Final answer
    x = 47.21

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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.