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Finding the Fourth Proportional to 1,278.21, 1,764 and 718.70

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Solution

The fourth proportional to 1,278.21, 1,764 and 718.70 is: 991.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,278.21 : 1,764 = 718.70 : x
  2. Step 2: Convert to fraction form
    1,278.21/1,764 = 718.70/x
  3. Step 3: Cross multiply
    1,278.21x = 1,764 × 718.70
  4. Step 4: Simplify right side
    1,278.21x = 1,267,786.80
  5. Step 5: Solve for x
    x = 1,267,786.80/1,278.21
  6. Step 6: Final answer
    x = 991.85

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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.