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Finding the Fourth Proportional to 1,005.78, 1,390.30 and 839.02

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Solution

The fourth proportional to 1,005.78, 1,390.30 and 839.02 is: 1,159.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,005.78 : 1,390.30 = 839.02 : x
  2. Step 2: Convert to fraction form
    1,005.78/1,390.30 = 839.02/x
  3. Step 3: Cross multiply
    1,005.78x = 1,390.30 × 839.02
  4. Step 4: Simplify right side
    1,005.78x = 1,166,486.54
  5. Step 5: Solve for x
    x = 1,166,486.54/1,005.78
  6. Step 6: Final answer
    x = 1,159.79

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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.