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Finding the Fourth Proportional to 1,278.70, 1,918.49 and 661.78

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Solution

The fourth proportional to 1,278.70, 1,918.49 and 661.78 is: 992.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,278.70 : 1,918.49 = 661.78 : x
  2. Step 2: Convert to fraction form
    1,278.70/1,918.49 = 661.78/x
  3. Step 3: Cross multiply
    1,278.70x = 1,918.49 × 661.78
  4. Step 4: Simplify right side
    1,278.70x = 1,269,618.31
  5. Step 5: Solve for x
    x = 1,269,618.31/1,278.70
  6. Step 6: Final answer
    x = 992.90

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.