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Finding the Fourth Proportional to 1,187.16, 1,638.90 and 721.56

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Solution

The fourth proportional to 1,187.16, 1,638.90 and 721.56 is: 996.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.16 : 1,638.90 = 721.56 : x
  2. Step 2: Convert to fraction form
    1,187.16/1,638.90 = 721.56/x
  3. Step 3: Cross multiply
    1,187.16x = 1,638.90 × 721.56
  4. Step 4: Simplify right side
    1,187.16x = 1,182,564.68
  5. Step 5: Solve for x
    x = 1,182,564.68/1,187.16
  6. Step 6: Final answer
    x = 996.13

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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.