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Finding the Fourth Proportional to 1,390.14, 1,917.93 and 991.87

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Solution

The fourth proportional to 1,390.14, 1,917.93 and 991.87 is: 1,368.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.14 : 1,917.93 = 991.87 : x
  2. Step 2: Convert to fraction form
    1,390.14/1,917.93 = 991.87/x
  3. Step 3: Cross multiply
    1,390.14x = 1,917.93 × 991.87
  4. Step 4: Simplify right side
    1,390.14x = 1,902,332.43
  5. Step 5: Solve for x
    x = 1,902,332.43/1,390.14
  6. Step 6: Final answer
    x = 1,368.45

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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.