A metalworker has a metal alloy that is 25% copper and another alloy that is 65% copper. How many kilograms of each alloy should the metalworker combine to create 60kg of a 57% copper alloy?

Adrawer contains 12 identical white socks, 18 identical black socks and 14 identical brown socks. what is the least number of socks you must choose, without looking, to be certain that you have chosen two socks of the same colour?

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297

The length of a rectangle plus its width is 24 cm. the area is 143 square cm. what are the length and width of the rectangle?