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Finding the Fourth Proportional to 642.40, 964.80 and 399.40

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Solution

The fourth proportional to 642.40, 964.80 and 399.40 is: 599.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.40 : 964.80 = 399.40 : x
  2. Step 2: Convert to fraction form
    642.40/964.80 = 399.40/x
  3. Step 3: Cross multiply
    642.40x = 964.80 × 399.40
  4. Step 4: Simplify right side
    642.40x = 385,341.12
  5. Step 5: Solve for x
    x = 385,341.12/642.40
  6. Step 6: Final answer
    x = 599.85

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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.