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Finding the Fourth Proportional to 921.80, 1,382.70 and 840.80

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Solution

The fourth proportional to 921.80, 1,382.70 and 840.80 is: 1,261.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.80 : 1,382.70 = 840.80 : x
  2. Step 2: Convert to fraction form
    921.80/1,382.70 = 840.80/x
  3. Step 3: Cross multiply
    921.80x = 1,382.70 × 840.80
  4. Step 4: Simplify right side
    921.80x = 1,162,574.16
  5. Step 5: Solve for x
    x = 1,162,574.16/921.80
  6. Step 6: Final answer
    x = 1,261.20

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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.