Sophie and simon are peeling a pile of potatoes for lunch in the cafeteria. sophie can peel all the potatoes by herself in 45 minutes, while it would take simon 30 minutes to do the job working alone. if sophie and simon work together to peel the potatoes, how long will it take them?

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.