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Finding the Fourth Proportional to 1,218, 1,680.42 and 720.81

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Solution

The fourth proportional to 1,218, 1,680.42 and 720.81 is: 994.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,218 : 1,680.42 = 720.81 : x
  2. Step 2: Convert to fraction form
    1,218/1,680.42 = 720.81/x
  3. Step 3: Cross multiply
    1,218x = 1,680.42 × 720.81
  4. Step 4: Simplify right side
    1,218x = 1,211,263.54
  5. Step 5: Solve for x
    x = 1,211,263.54/1,218
  6. Step 6: Final answer
    x = 994.47

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.