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Finding the Fourth Proportional to 918.87, 1,268.42 and 639.51

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Solution

The fourth proportional to 918.87, 1,268.42 and 639.51 is: 882.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    918.87 : 1,268.42 = 639.51 : x
  2. Step 2: Convert to fraction form
    918.87/1,268.42 = 639.51/x
  3. Step 3: Cross multiply
    918.87x = 1,268.42 × 639.51
  4. Step 4: Simplify right side
    918.87x = 811,164.08
  5. Step 5: Solve for x
    x = 811,164.08/918.87
  6. Step 6: Final answer
    x = 882.78

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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.