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Finding the Fourth Proportional to 1,391.64, 1,917.80 and 998

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Solution

The fourth proportional to 1,391.64, 1,917.80 and 998 is: 1,375.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.64 : 1,917.80 = 998 : x
  2. Step 2: Convert to fraction form
    1,391.64/1,917.80 = 998/x
  3. Step 3: Cross multiply
    1,391.64x = 1,917.80 × 998
  4. Step 4: Simplify right side
    1,391.64x = 1,913,964.40
  5. Step 5: Solve for x
    x = 1,913,964.40/1,391.64
  6. Step 6: Final answer
    x = 1,375.33

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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.