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Finding the Fourth Proportional to 990.40, 1,366.70 and 641.28

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Solution

The fourth proportional to 990.40, 1,366.70 and 641.28 is: 884.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.40 : 1,366.70 = 641.28 : x
  2. Step 2: Convert to fraction form
    990.40/1,366.70 = 641.28/x
  3. Step 3: Cross multiply
    990.40x = 1,366.70 × 641.28
  4. Step 4: Simplify right side
    990.40x = 876,437.38
  5. Step 5: Solve for x
    x = 876,437.38/990.40
  6. Step 6: Final answer
    x = 884.93

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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.