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Finding the Fourth Proportional to 811.72, 1,215.15 and 690.22

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Solution

The fourth proportional to 811.72, 1,215.15 and 690.22 is: 1,033.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.72 : 1,215.15 = 690.22 : x
  2. Step 2: Convert to fraction form
    811.72/1,215.15 = 690.22/x
  3. Step 3: Cross multiply
    811.72x = 1,215.15 × 690.22
  4. Step 4: Simplify right side
    811.72x = 838,720.83
  5. Step 5: Solve for x
    x = 838,720.83/811.72
  6. Step 6: Final answer
    x = 1,033.26

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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.