Question

a certain type of light bulb has an average of 700 hours, with a standard deviation of 150 hours. The length of life of the bulb can be closely approximated by a normal curve. An amusement park buys and installs 40,000 such bulbs. Find the total number that can ve expected to last more than 640 hours.

This Question: 4 pts 3 of 42 (0 complete This Test: 150 pts possible o A certain type of light bulb has an average life of 700 hours, with a standard deviation of 150 hours. The length of title of the but can be closely approximated by anomal curve. An amusement park buys and instals 40,000 such bulbs Find the total number that can be expected to last more than 10 hours Click here to view the standard romantie. Click here to view of the standard roma table The number of im bubs that can be expected to fost more than 640 hours in

Answer 1

Solution: - mean(u) - 700 hours Standard deviation (6) - 150 hours Xa A 690 hours Za X-4 640-700 ISO -0.4 640 Pla x>400) 0.34458 than more 0.655 42 Expected number of bulb that lasts 640 hours - 0.655 42 x 40,000 - 26216.8 3 26217 Ans.