The acidity in a swimming pool is considered normal if the average of three pH readings, p, is defined such that
7.0< p < 7.8. If the first two readings are 7.2 and 7.6,
which value for the third reading will result in an overall
rating of normal?

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.