Four friends are out for a walk at night and come to an old bridge. it isn’t safe to cross the bridge without a flashlight, and only two people can cross at a time. they only have one flashlight. if the same person carries the flashlight the entire time, what is the minimum number of times that person will have to cross the bridge in order for the entire group to get to the other side?

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.