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Finding the Fourth Proportional to 812.84, 1,121.46 and 678.40

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Solution

The fourth proportional to 812.84, 1,121.46 and 678.40 is: 935.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.84 : 1,121.46 = 678.40 : x
  2. Step 2: Convert to fraction form
    812.84/1,121.46 = 678.40/x
  3. Step 3: Cross multiply
    812.84x = 1,121.46 × 678.40
  4. Step 4: Simplify right side
    812.84x = 760,798.46
  5. Step 5: Solve for x
    x = 760,798.46/812.84
  6. Step 6: Final answer
    x = 935.98

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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.