The weight, w, of a spring in pounds is given by 0.9 times the square root of the energy, e, stored by the spring in joules. if the energy stored by the spring is 12 joules, what is the approximate weight of the spring in pounds?

We just started the introduction into circles and i have no idea how to do this.

What is the interquartile range of this data set? 2, 5, 9, 11, 18, 30, 42, 48, 55, 73, 81

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?