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Finding the Fourth Proportional to 1,390.69, 2,085.42 and 660.47

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Solution

The fourth proportional to 1,390.69, 2,085.42 and 660.47 is: 990.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.69 : 2,085.42 = 660.47 : x
  2. Step 2: Convert to fraction form
    1,390.69/2,085.42 = 660.47/x
  3. Step 3: Cross multiply
    1,390.69x = 2,085.42 × 660.47
  4. Step 4: Simplify right side
    1,390.69x = 1,377,357.35
  5. Step 5: Solve for x
    x = 1,377,357.35/1,390.69
  6. Step 6: Final answer
    x = 990.42

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.