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Finding the Fourth Proportional to 1,390, 1,918.20 and 769.04

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Solution

The fourth proportional to 1,390, 1,918.20 and 769.04 is: 1,061.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390 : 1,918.20 = 769.04 : x
  2. Step 2: Convert to fraction form
    1,390/1,918.20 = 769.04/x
  3. Step 3: Cross multiply
    1,390x = 1,918.20 × 769.04
  4. Step 4: Simplify right side
    1,390x = 1,475,172.53
  5. Step 5: Solve for x
    x = 1,475,172.53/1,390
  6. Step 6: Final answer
    x = 1,061.28

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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.