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Finding the Fourth Proportional to 990.12, 1,485.72 and 987

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Solution

The fourth proportional to 990.12, 1,485.72 and 987 is: 1,481.04

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.12 : 1,485.72 = 987 : x
  2. Step 2: Convert to fraction form
    990.12/1,485.72 = 987/x
  3. Step 3: Cross multiply
    990.12x = 1,485.72 × 987
  4. Step 4: Simplify right side
    990.12x = 1,466,405.64
  5. Step 5: Solve for x
    x = 1,466,405.64/990.12
  6. Step 6: Final answer
    x = 1,481.04

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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.