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Finding the Fourth Proportional to 879.40, 1,215.30 and 721.79

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Solution

The fourth proportional to 879.40, 1,215.30 and 721.79 is: 997.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    879.40 : 1,215.30 = 721.79 : x
  2. Step 2: Convert to fraction form
    879.40/1,215.30 = 721.79/x
  3. Step 3: Cross multiply
    879.40x = 1,215.30 × 721.79
  4. Step 4: Simplify right side
    879.40x = 877,191.39
  5. Step 5: Solve for x
    x = 877,191.39/879.40
  6. Step 6: Final answer
    x = 997.49

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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.