Two lighthouses can be seen from the top of a hill. the frist flashes once every 6 seconds and the otherflashes once every 15 seconds.
if they flash simultaneously, how long is it until they flash again at the same time?

According to a study conducted in 2015, 18% of shoppers said that they prefer to buy generic instead of name-brand products. suppose that in a recent sample of 1500 shoppers, 315 stated that they prefer to buy generic instead of name-brand products. at a 5% significance level, can you conclude that the proportion of all shoppers who currently prefer to buy generic instead of name-brand products is higher than .18? use both the p-value and the critical-value approaches.