The number of bulbs expected to be defective in a case of 450 is 30.
Number of bulbs of sample = 30
Defective bulb = 2
As the sample was representative, it means that every sample of 30 bulbs will have 2 defective bulbs.
The ratio of defective bulbs to sample is 2: 30
Total bulbs = 450
Defective bulbs = x
The ratio of total bulbs to defective bulbs x: 450
Therefore,
[tex]$2: 30:: x: 450$[/tex]
Product of Mean = Product of Extremes
[tex]&30 * x=450 * 2 \\[/tex]
[tex]&30 x=900[/tex]
Dividing both sides by 30
[tex]&\frac{30 x}{30}=\frac{900}{30} \\[/tex]
[tex]&x=30[/tex]
The number of bulbs expected to be defective in a case of 450 is 30.
Therefore, the correct answer is option A.) 30.
To learn more about ratios
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