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Finding the Fourth Proportional to 990.36, 1,485.68 and 639.24

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Solution

The fourth proportional to 990.36, 1,485.68 and 639.24 is: 958.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.36 : 1,485.68 = 639.24 : x
  2. Step 2: Convert to fraction form
    990.36/1,485.68 = 639.24/x
  3. Step 3: Cross multiply
    990.36x = 1,485.68 × 639.24
  4. Step 4: Simplify right side
    990.36x = 949,705.67
  5. Step 5: Solve for x
    x = 949,705.67/990.36
  6. Step 6: Final answer
    x = 958.95

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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.