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Finding the Fourth Proportional to 990.64, 1,367.96 and 642.16

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Solution

The fourth proportional to 990.64, 1,367.96 and 642.16 is: 886.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.64 : 1,367.96 = 642.16 : x
  2. Step 2: Convert to fraction form
    990.64/1,367.96 = 642.16/x
  3. Step 3: Cross multiply
    990.64x = 1,367.96 × 642.16
  4. Step 4: Simplify right side
    990.64x = 878,449.19
  5. Step 5: Solve for x
    x = 878,449.19/990.64
  6. Step 6: Final answer
    x = 886.75

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.