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Finding the Fourth Proportional to 1,390.79, 1,919.31 and 769.79

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Solution

The fourth proportional to 1,390.79, 1,919.31 and 769.79 is: 1,062.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.79 : 1,919.31 = 769.79 : x
  2. Step 2: Convert to fraction form
    1,390.79/1,919.31 = 769.79/x
  3. Step 3: Cross multiply
    1,390.79x = 1,919.31 × 769.79
  4. Step 4: Simplify right side
    1,390.79x = 1,477,465.64
  5. Step 5: Solve for x
    x = 1,477,465.64/1,390.79
  6. Step 6: Final answer
    x = 1,062.32

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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.