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Finding the Fourth Proportional to 1,121.40, 1,681.80 and 390.48

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Solution

The fourth proportional to 1,121.40, 1,681.80 and 390.48 is: 585.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.40 : 1,681.80 = 390.48 : x
  2. Step 2: Convert to fraction form
    1,121.40/1,681.80 = 390.48/x
  3. Step 3: Cross multiply
    1,121.40x = 1,681.80 × 390.48
  4. Step 4: Simplify right side
    1,121.40x = 656,709.26
  5. Step 5: Solve for x
    x = 656,709.26/1,121.40
  6. Step 6: Final answer
    x = 585.62

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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.