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Finding the Fourth Proportional to 1,211.15, 1,671.39 and 687.20

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Solution

The fourth proportional to 1,211.15, 1,671.39 and 687.20 is: 948.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,211.15 : 1,671.39 = 687.20 : x
  2. Step 2: Convert to fraction form
    1,211.15/1,671.39 = 687.20/x
  3. Step 3: Cross multiply
    1,211.15x = 1,671.39 × 687.20
  4. Step 4: Simplify right side
    1,211.15x = 1,148,579.21
  5. Step 5: Solve for x
    x = 1,148,579.21/1,211.15
  6. Step 6: Final answer
    x = 948.34

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Half scale
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Double scale
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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.