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Finding the Fourth Proportional to 1,391.30, 1,919.40 and 919.70

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Solution

The fourth proportional to 1,391.30, 1,919.40 and 919.70 is: 1,268.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.30 : 1,919.40 = 919.70 : x
  2. Step 2: Convert to fraction form
    1,391.30/1,919.40 = 919.70/x
  3. Step 3: Cross multiply
    1,391.30x = 1,919.40 × 919.70
  4. Step 4: Simplify right side
    1,391.30x = 1,765,272.18
  5. Step 5: Solve for x
    x = 1,765,272.18/1,391.30
  6. Step 6: Final answer
    x = 1,268.79

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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.