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Finding the Fourth Proportional to 1,287.67, 1,777 and 698.21

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Solution

The fourth proportional to 1,287.67, 1,777 and 698.21 is: 963.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.67 : 1,777 = 698.21 : x
  2. Step 2: Convert to fraction form
    1,287.67/1,777 = 698.21/x
  3. Step 3: Cross multiply
    1,287.67x = 1,777 × 698.21
  4. Step 4: Simplify right side
    1,287.67x = 1,240,719.17
  5. Step 5: Solve for x
    x = 1,240,719.17/1,287.67
  6. Step 6: Final answer
    x = 963.54

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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.