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Finding the Fourth Proportional to 1,379.28, 2,069.28 and 405.40

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Solution

The fourth proportional to 1,379.28, 2,069.28 and 405.40 is: 608.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,379.28 : 2,069.28 = 405.40 : x
  2. Step 2: Convert to fraction form
    1,379.28/2,069.28 = 405.40/x
  3. Step 3: Cross multiply
    1,379.28x = 2,069.28 × 405.40
  4. Step 4: Simplify right side
    1,379.28x = 838,886.11
  5. Step 5: Solve for x
    x = 838,886.11/1,379.28
  6. Step 6: Final answer
    x = 608.21

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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.