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Finding the Fourth Proportional to 1,380.45, 2,070.81 and 687

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Solution

The fourth proportional to 1,380.45, 2,070.81 and 687 is: 1,030.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,380.45 : 2,070.81 = 687 : x
  2. Step 2: Convert to fraction form
    1,380.45/2,070.81 = 687/x
  3. Step 3: Cross multiply
    1,380.45x = 2,070.81 × 687
  4. Step 4: Simplify right side
    1,380.45x = 1,422,646.47
  5. Step 5: Solve for x
    x = 1,422,646.47/1,380.45
  6. Step 6: Final answer
    x = 1,030.57

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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.