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Finding the Fourth Proportional to 1,321.72, 1,979.74 and 858.15

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Solution

The fourth proportional to 1,321.72, 1,979.74 and 858.15 is: 1,285.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,321.72 : 1,979.74 = 858.15 : x
  2. Step 2: Convert to fraction form
    1,321.72/1,979.74 = 858.15/x
  3. Step 3: Cross multiply
    1,321.72x = 1,979.74 × 858.15
  4. Step 4: Simplify right side
    1,321.72x = 1,698,913.88
  5. Step 5: Solve for x
    x = 1,698,913.88/1,321.72
  6. Step 6: Final answer
    x = 1,285.38

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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.