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Finding the Fourth Proportional to 85.64, 128.40 and 45.02

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Solution

The fourth proportional to 85.64, 128.40 and 45.02 is: 67.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.64 : 128.40 = 45.02 : x
  2. Step 2: Convert to fraction form
    85.64/128.40 = 45.02/x
  3. Step 3: Cross multiply
    85.64x = 128.40 × 45.02
  4. Step 4: Simplify right side
    85.64x = 5,780.57
  5. Step 5: Solve for x
    x = 5,780.57/85.64
  6. Step 6: Final answer
    x = 67.50

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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.