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Finding the Fourth Proportional to 66.21, 91.38 and 42.90

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Solution

The fourth proportional to 66.21, 91.38 and 42.90 is: 59.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.21 : 91.38 = 42.90 : x
  2. Step 2: Convert to fraction form
    66.21/91.38 = 42.90/x
  3. Step 3: Cross multiply
    66.21x = 91.38 × 42.90
  4. Step 4: Simplify right side
    66.21x = 3,920.20
  5. Step 5: Solve for x
    x = 3,920.20/66.21
  6. Step 6: Final answer
    x = 59.21

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.