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Finding the Fourth Proportional to 1,285.29, 1,771.95 and 987

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Solution

The fourth proportional to 1,285.29, 1,771.95 and 987 is: 1,360.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,285.29 : 1,771.95 = 987 : x
  2. Step 2: Convert to fraction form
    1,285.29/1,771.95 = 987/x
  3. Step 3: Cross multiply
    1,285.29x = 1,771.95 × 987
  4. Step 4: Simplify right side
    1,285.29x = 1,748,914.65
  5. Step 5: Solve for x
    x = 1,748,914.65/1,285.29
  6. Step 6: Final answer
    x = 1,360.72

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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.