A) \[\frac{1}{5}\]
B) \[\frac{7}{10}\]
C) \[\frac{1}{10}\]
D) \[\frac{3}{10}\]
Correct Answer: B
Solution :
Given total number of bolts = 600 Number of large bolts = 20% of 600 \[=\frac{20}{100}\times 600=120\] Number of small bolts = 10% of 600 \[=\frac{10}{100}\times 600=60\] \[\therefore \]Number of suitable bolts \[=600-120-60=420\] \[\therefore \]Probability of selecting suitable bolt \[=\frac{420}{600}=\frac{7}{10}\] Alternative Method Given total number of bolts = 600 Number of larger bolts = 20% of 600 \[=\frac{20}{100}\times 600=120\] \[\therefore \]Probability of selecting large bolt \[=\frac{120}{600}\] ?.(i) Number of small bolts = 10% of 600 \[=\frac{10}{100}\times 600=60\] \[\therefore \]Probability of selecting small bolts \[=\frac{60}{600}\] ?. (ii) \[\therefore \] Probability of getting suitable bolt \[=1-\left( \frac{120}{600}+\frac{60}{600} \right)\] \[=\frac{600-120-60}{600}=\frac{420}{600}=\frac{7}{10}\]
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