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Finding the Fourth Proportional to 811.20, 1,215.60 and 688.80

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Solution

The fourth proportional to 811.20, 1,215.60 and 688.80 is: 1,032.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.20 : 1,215.60 = 688.80 : x
  2. Step 2: Convert to fraction form
    811.20/1,215.60 = 688.80/x
  3. Step 3: Cross multiply
    811.20x = 1,215.60 × 688.80
  4. Step 4: Simplify right side
    811.20x = 837,305.28
  5. Step 5: Solve for x
    x = 837,305.28/811.20
  6. Step 6: Final answer
    x = 1,032.18

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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.