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Finding the Fourth Proportional to 678.12, 935.76 and 398.40

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Solution

The fourth proportional to 678.12, 935.76 and 398.40 is: 549.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.12 : 935.76 = 398.40 : x
  2. Step 2: Convert to fraction form
    678.12/935.76 = 398.40/x
  3. Step 3: Cross multiply
    678.12x = 935.76 × 398.40
  4. Step 4: Simplify right side
    678.12x = 372,806.78
  5. Step 5: Solve for x
    x = 372,806.78/678.12
  6. Step 6: Final answer
    x = 549.77

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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.