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Finding the Fourth Proportional to 811.51, 1,215.72 and 420.94

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Solution

The fourth proportional to 811.51, 1,215.72 and 420.94 is: 630.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.51 : 1,215.72 = 420.94 : x
  2. Step 2: Convert to fraction form
    811.51/1,215.72 = 420.94/x
  3. Step 3: Cross multiply
    811.51x = 1,215.72 × 420.94
  4. Step 4: Simplify right side
    811.51x = 511,745.18
  5. Step 5: Solve for x
    x = 511,745.18/811.51
  6. Step 6: Final answer
    x = 630.61

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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.