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Finding the Fourth Proportional to 990.40, 1,485.81 and 287.61

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Solution

The fourth proportional to 990.40, 1,485.81 and 287.61 is: 431.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.40 : 1,485.81 = 287.61 : x
  2. Step 2: Convert to fraction form
    990.40/1,485.81 = 287.61/x
  3. Step 3: Cross multiply
    990.40x = 1,485.81 × 287.61
  4. Step 4: Simplify right side
    990.40x = 427,333.81
  5. Step 5: Solve for x
    x = 427,333.81/990.40
  6. Step 6: Final answer
    x = 431.48

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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.