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Finding the Fourth Proportional to 990.78, 1,485.14 and 644.36

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Solution

The fourth proportional to 990.78, 1,485.14 and 644.36 is: 965.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.78 : 1,485.14 = 644.36 : x
  2. Step 2: Convert to fraction form
    990.78/1,485.14 = 644.36/x
  3. Step 3: Cross multiply
    990.78x = 1,485.14 × 644.36
  4. Step 4: Simplify right side
    990.78x = 956,954.16
  5. Step 5: Solve for x
    x = 956,954.16/990.78
  6. Step 6: Final answer
    x = 965.86

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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.