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Finding the Fourth Proportional to 85.60, 128.38 and 31.48

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Solution

The fourth proportional to 85.60, 128.38 and 31.48 is: 47.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.60 : 128.38 = 31.48 : x
  2. Step 2: Convert to fraction form
    85.60/128.38 = 31.48/x
  3. Step 3: Cross multiply
    85.60x = 128.38 × 31.48
  4. Step 4: Simplify right side
    85.60x = 4,041.06
  5. Step 5: Solve for x
    x = 4,041.06/85.60
  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.