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Finding the Fourth Proportional to 1,390.13, 1,918.83 and 919.31

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Solution

The fourth proportional to 1,390.13, 1,918.83 and 919.31 is: 1,268.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.13 : 1,918.83 = 919.31 : x
  2. Step 2: Convert to fraction form
    1,390.13/1,918.83 = 919.31/x
  3. Step 3: Cross multiply
    1,390.13x = 1,918.83 × 919.31
  4. Step 4: Simplify right side
    1,390.13x = 1,763,990.01
  5. Step 5: Solve for x
    x = 1,763,990.01/1,390.13
  6. Step 6: Final answer
    x = 1,268.94

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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.