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Finding the Fourth Proportional to 1,328.68, 1,989.96 and 780.70

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Solution

The fourth proportional to 1,328.68, 1,989.96 and 780.70 is: 1,169.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,328.68 : 1,989.96 = 780.70 : x
  2. Step 2: Convert to fraction form
    1,328.68/1,989.96 = 780.70/x
  3. Step 3: Cross multiply
    1,328.68x = 1,989.96 × 780.70
  4. Step 4: Simplify right side
    1,328.68x = 1,553,561.77
  5. Step 5: Solve for x
    x = 1,553,561.77/1,328.68
  6. Step 6: Final answer
    x = 1,169.25

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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.