Mary is 16 years old. She is 4 times older than her brother. How old will Mary be when she is twice his age

There is a lake on the surface of which water lilies float. The number of lilies doubles daily. If it takes 48 days to completely occupy the entire area of the lake, how many days will it take to occupy the floor of the lake

There are 5 machines that make 5 parts in 5 minutes. How long does it take to make 100 parts on 100 machines

The store reduces the price of one product by 20 percent. How many percent do you need to raise to the percentage to get the original price

Which fraction is the biggest

To which hexagon below can a dot be added so that both dots then meet the same conditions as in the hexagon above