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Finding the Fourth Proportional to 1,290.78, 1,779.78 and 936

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Solution

The fourth proportional to 1,290.78, 1,779.78 and 936 is: 1,290.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.78 : 1,779.78 = 936 : x
  2. Step 2: Convert to fraction form
    1,290.78/1,779.78 = 936/x
  3. Step 3: Cross multiply
    1,290.78x = 1,779.78 × 936
  4. Step 4: Simplify right side
    1,290.78x = 1,665,874.08
  5. Step 5: Solve for x
    x = 1,665,874.08/1,290.78
  6. Step 6: Final answer
    x = 1,290.59

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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.