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Finding the Fourth Proportional to 1,120.71, 1,680.75 and 390.09

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Solution

The fourth proportional to 1,120.71, 1,680.75 and 390.09 is: 585.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.71 : 1,680.75 = 390.09 : x
  2. Step 2: Convert to fraction form
    1,120.71/1,680.75 = 390.09/x
  3. Step 3: Cross multiply
    1,120.71x = 1,680.75 × 390.09
  4. Step 4: Simplify right side
    1,120.71x = 655,643.77
  5. Step 5: Solve for x
    x = 655,643.77/1,120.71
  6. Step 6: Final answer
    x = 585.03

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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.