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Finding the Fourth Proportional to 1,389.79, 2,084.69 and 639.23

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Solution

The fourth proportional to 1,389.79, 2,084.69 and 639.23 is: 958.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,389.79 : 2,084.69 = 639.23 : x
  2. Step 2: Convert to fraction form
    1,389.79/2,084.69 = 639.23/x
  3. Step 3: Cross multiply
    1,389.79x = 2,084.69 × 639.23
  4. Step 4: Simplify right side
    1,389.79x = 1,332,583.97
  5. Step 5: Solve for x
    x = 1,332,583.97/1,389.79
  6. Step 6: Final answer
    x = 958.84

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.