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Finding the Fourth Proportional to 987.40, 1,361.92 and 637.76

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Solution

The fourth proportional to 987.40, 1,361.92 and 637.76 is: 879.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.40 : 1,361.92 = 637.76 : x
  2. Step 2: Convert to fraction form
    987.40/1,361.92 = 637.76/x
  3. Step 3: Cross multiply
    987.40x = 1,361.92 × 637.76
  4. Step 4: Simplify right side
    987.40x = 868,578.10
  5. Step 5: Solve for x
    x = 868,578.10/987.40
  6. Step 6: Final answer
    x = 879.66

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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.