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Finding the Fourth Proportional to 1,421.09, 1,960.63 and 831.20

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Solution

The fourth proportional to 1,421.09, 1,960.63 and 831.20 is: 1,146.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,421.09 : 1,960.63 = 831.20 : x
  2. Step 2: Convert to fraction form
    1,421.09/1,960.63 = 831.20/x
  3. Step 3: Cross multiply
    1,421.09x = 1,960.63 × 831.20
  4. Step 4: Simplify right side
    1,421.09x = 1,629,678.48
  5. Step 5: Solve for x
    x = 1,629,678.48/1,421.09
  6. Step 6: Final answer
    x = 1,146.78

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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.