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Finding the Fourth Proportional to 987.61, 1,361.46 and 811.57

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Solution

The fourth proportional to 987.61, 1,361.46 and 811.57 is: 1,118.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.61 : 1,361.46 = 811.57 : x
  2. Step 2: Convert to fraction form
    987.61/1,361.46 = 811.57/x
  3. Step 3: Cross multiply
    987.61x = 1,361.46 × 811.57
  4. Step 4: Simplify right side
    987.61x = 1,104,920.09
  5. Step 5: Solve for x
    x = 1,104,920.09/987.61
  6. Step 6: Final answer
    x = 1,118.78

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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.