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Finding the Fourth Proportional to 990.72, 1,485.60 and 665.76

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Solution

The fourth proportional to 990.72, 1,485.60 and 665.76 is: 998.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.72 : 1,485.60 = 665.76 : x
  2. Step 2: Convert to fraction form
    990.72/1,485.60 = 665.76/x
  3. Step 3: Cross multiply
    990.72x = 1,485.60 × 665.76
  4. Step 4: Simplify right side
    990.72x = 989,053.06
  5. Step 5: Solve for x
    x = 989,053.06/990.72
  6. Step 6: Final answer
    x = 998.32

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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.