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Finding the Fourth Proportional to 1,290.81, 1,781.51 and 731.51

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Solution

The fourth proportional to 1,290.81, 1,781.51 and 731.51 is: 1,009.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.81 : 1,781.51 = 731.51 : x
  2. Step 2: Convert to fraction form
    1,290.81/1,781.51 = 731.51/x
  3. Step 3: Cross multiply
    1,290.81x = 1,781.51 × 731.51
  4. Step 4: Simplify right side
    1,290.81x = 1,303,179.82
  5. Step 5: Solve for x
    x = 1,303,179.82/1,290.81
  6. Step 6: Final answer
    x = 1,009.58

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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.