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Finding the Fourth Proportional to 831.06, 1,247.40 and 639.90

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Solution

The fourth proportional to 831.06, 1,247.40 and 639.90 is: 960.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    831.06 : 1,247.40 = 639.90 : x
  2. Step 2: Convert to fraction form
    831.06/1,247.40 = 639.90/x
  3. Step 3: Cross multiply
    831.06x = 1,247.40 × 639.90
  4. Step 4: Simplify right side
    831.06x = 798,211.26
  5. Step 5: Solve for x
    x = 798,211.26/831.06
  6. Step 6: Final answer
    x = 960.47

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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.