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Finding the Fourth Proportional to 1,380.40, 2,070.13 and 687.40

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Solution

The fourth proportional to 1,380.40, 2,070.13 and 687.40 is: 1,030.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,380.40 : 2,070.13 = 687.40 : x
  2. Step 2: Convert to fraction form
    1,380.40/2,070.13 = 687.40/x
  3. Step 3: Cross multiply
    1,380.40x = 2,070.13 × 687.40
  4. Step 4: Simplify right side
    1,380.40x = 1,423,007.36
  5. Step 5: Solve for x
    x = 1,423,007.36/1,380.40
  6. Step 6: Final answer
    x = 1,030.87

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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.