The lifespans of certain batteries are normally distributed. It is found that 15% of battery/less than 30 hours and 10% of batteries last more than 50 hours. Find the mean and standard deviation of the lifespan of the batteries

According to modern science, earth is about 4.5 billion years old and written human history extends back about 10,000 years. suppose the entire history of earth is represented with a 10-meter-long timeline, with the birth of earth on one end and today at the other end.

What is the prime factorization of 230

The population of a small rural town in the year 2006 was 2,459. the population can be modeled by the function below, where f(x residents and t is the number of years elapsed since 2006. f(t) = 2,459(0.92)