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Finding the Fourth Proportional to 1,370.78, 1,891.21 and 780.90

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Solution

The fourth proportional to 1,370.78, 1,891.21 and 780.90 is: 1,077.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,370.78 : 1,891.21 = 780.90 : x
  2. Step 2: Convert to fraction form
    1,370.78/1,891.21 = 780.90/x
  3. Step 3: Cross multiply
    1,370.78x = 1,891.21 × 780.90
  4. Step 4: Simplify right side
    1,370.78x = 1,476,845.89
  5. Step 5: Solve for x
    x = 1,476,845.89/1,370.78
  6. Step 6: Final answer
    x = 1,077.38

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1.5x scale

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.