弱问OG里的一道数学题

laranli

213. In an electric circuit, two resistors with resistances x
and y are connected in parallel. In this case, if r is the
combined resistance of these two resistors, then the
reciprocal of r is equal to the sum of the reciprocals of
x and y. What is r in terms of x and y ?
(A) xy
(B) x + y
(C) 1/x + y
(D)xy/x + y
(E)x + y/xy
答案D。reciprocal of r is equal to the sum of the reciprocals of x and y ，个人认为此句应当理解为1/r=1/x+y；但OG似乎理解为1/r=1/x+1/y。求教各位牛牛，这句话到底表达啥意思？

serenana

他问得是the sum of the reciprocals of x,y是两个先倒再加，而你说的那个是 the reciprocals of the sum of x,y~~我是这么理解的~~非nn一枚~~

shishmily

他问得是the sum of the reciprocals of x,y是两个先倒再加，而你说的那个是 the reciprocals of the sum of x,y~~我是这么理解的~~非nn一枚~~

-- by 会员 serenana (2011/10/26 21:27:03)

同意楼上，按题得意思就是电路的电阻并联啊~~
就是1/r=1/x+1/y~~

cq168088

直接背出高中物理电阻并联公式就毫无压力了。

laranli

谢谢解答哈

大叮田

文科生表示第一次看到reciprocal就给跪了。