有没有比ETS的数学思路更好的解法?
这是OG里面的一道题(P402)Areadinglistforahumanitiescourseconsistsof10books,ofwhich4arebiographiesandtherestarenovels.Eachstudentisrequiredtoreadaselectionof4booksfromthelist,including2ormorebiographies.Howmanyselectionsof4bookssatisfytherequirements?A90B115C130D144E195OG的官方解法太复杂了,有没有哪位有比较好的解法?