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Finding the Fourth Proportional to 1,287.21, 1,922.98 and 821.28

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Solution

The fourth proportional to 1,287.21, 1,922.98 and 821.28 is: 1,226.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.21 : 1,922.98 = 821.28 : x
  2. Step 2: Convert to fraction form
    1,287.21/1,922.98 = 821.28/x
  3. Step 3: Cross multiply
    1,287.21x = 1,922.98 × 821.28
  4. Step 4: Simplify right side
    1,287.21x = 1,579,305.01
  5. Step 5: Solve for x
    x = 1,579,305.01/1,287.21
  6. Step 6: Final answer
    x = 1,226.92

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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 (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.