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Finding the Fourth Proportional to 1,209, 1,668.56 and 685.20

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Solution

The fourth proportional to 1,209, 1,668.56 and 685.20 is: 945.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,209 : 1,668.56 = 685.20 : x
  2. Step 2: Convert to fraction form
    1,209/1,668.56 = 685.20/x
  3. Step 3: Cross multiply
    1,209x = 1,668.56 × 685.20
  4. Step 4: Simplify right side
    1,209x = 1,143,293.89
  5. Step 5: Solve for x
    x = 1,143,293.89/1,209
  6. Step 6: Final answer
    x = 945.65

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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.