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Finding the Fourth Proportional to 1,390.49, 1,918.64 and 831.18

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Solution

The fourth proportional to 1,390.49, 1,918.64 and 831.18 is: 1,146.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.49 : 1,918.64 = 831.18 : x
  2. Step 2: Convert to fraction form
    1,390.49/1,918.64 = 831.18/x
  3. Step 3: Cross multiply
    1,390.49x = 1,918.64 × 831.18
  4. Step 4: Simplify right side
    1,390.49x = 1,594,731.04
  5. Step 5: Solve for x
    x = 1,594,731.04/1,390.49
  6. Step 6: Final answer
    x = 1,146.89

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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.