Interactive practice questions
The operating times of phone batteries are approximately normally distributed with mean $34$34 hours and a standard deviation of $4$4 hours. Answer the following questions using your calculator:
Approximately what percentage of batteries last between $33$33 and $38$38 hours?
Round your answer to the nearest percent.
Approximately what percentage of batteries last between $28$28 hours and $41$41 hours?
Any battery that lasts less than $23$23 hours is deemed faulty. If a company manufactured $51000$51000 batteries, approximately how many batteries would they be able to sell? Round your answer to the nearest integer.
The height of sunflowers is approximately normally distributed, with a mean height of $1.6$1.6 m and a standard deviation of $8$8 cm.
A machine is set for the production of cylinders of mean diameter $5.06$5.06 cm, with standard deviation $0.016$0.016 cm.
A weather station records temperatures normally distributed with a mean of $28$28$^{\circ}$∘C and a standard deviation of $3.3$3.3$^{\circ}$∘C.
The temperatures were converted to Kelvin using the rule $Y=X+273.15$Y=X+273.15 where $X$X is the temperature in Celsius and $Y$Y is the temperature in Kelvin.