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Finding the Fourth Proportional to 1,389, 1,916.88 and 768

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Solution

The fourth proportional to 1,389, 1,916.88 and 768 is: 1,059.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,389 : 1,916.88 = 768 : x
  2. Step 2: Convert to fraction form
    1,389/1,916.88 = 768/x
  3. Step 3: Cross multiply
    1,389x = 1,916.88 × 768
  4. Step 4: Simplify right side
    1,389x = 1,472,163.84
  5. Step 5: Solve for x
    x = 1,472,163.84/1,389
  6. Step 6: Final answer
    x = 1,059.87

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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.