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Finding the Fourth Proportional to 1,007, 1,390.40 and 811.40

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Solution

The fourth proportional to 1,007, 1,390.40 and 811.40 is: 1,120.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,007 : 1,390.40 = 811.40 : x
  2. Step 2: Convert to fraction form
    1,007/1,390.40 = 811.40/x
  3. Step 3: Cross multiply
    1,007x = 1,390.40 × 811.40
  4. Step 4: Simplify right side
    1,007x = 1,128,170.56
  5. Step 5: Solve for x
    x = 1,128,170.56/1,007
  6. Step 6: Final answer
    x = 1,120.33

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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.