数学题：甲、乙、丙、丁四人共植树60棵。甲植树的棵数是其余三人的二分之一，乙植树的棵数是其余三人的三分之一，丙植树的棵数是其余三人的四分之一，丁植树多少棵？

数学题解答：

由“甲植树的棵数是其余三人的二分之一”，可以把甲植树棵数看成1份，而其余三人合起来是2份。这样便可以算出甲植树棵数占四人的几分之几？1÷(1+2)=1/3。

同样道理，乙、丙植树棵数分别占四人总数的几分之几，也可以这样算出来。1÷(1+3)=1/4，1÷(1+4)=1/5

最后算出丁植树棵数占四人总数的几分之几？1 – １/３ – 1/4 -1/5 = 13/60

丁植树的棵数：60× 13/60 = 13(棵)

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