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Finding the Fourth Proportional to 51.90, 78.12 and 45.21

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Solution

The fourth proportional to 51.90, 78.12 and 45.21 is: 68.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    51.90 : 78.12 = 45.21 : x
  2. Step 2: Convert to fraction form
    51.90/78.12 = 45.21/x
  3. Step 3: Cross multiply
    51.90x = 78.12 × 45.21
  4. Step 4: Simplify right side
    51.90x = 3,531.81
  5. Step 5: Solve for x
    x = 3,531.81/51.90
  6. Step 6: Final answer
    x = 68.05

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.