math problem?

1 ⤊

1/x+1/y=4 and xy=3 the average (arithmetic mean) of x and y is?
A 3/2
B 2
C 4
D 6
E 12

2007-04-10 16:39:18 · 4 answers · asked by liangjizong22 1 in Science & Mathematics ➔ Mathematics

(y + x)/ xy = 4

(y + x)/ 3 = 4

(x+y)/2 = 6

Ana

2007-04-10 16:43:33 · answer #1 · answered by MathTutor 6 · 0⤊ 0⤋

2007-04-10 23:45:46 · answer #2 · answered by ganesan 2 · 0⤊ 0⤋

1/x + 1/y = 4 Multiply both sides by x y.
y + x = 4 x y replace x y with 3

y + x = 4 ( 3 )
y + x = 12 Therefore average is 6 to total 12.
Answer D.

2007-04-10 23:48:54 · answer #3 · answered by Skeptic 7 · 0⤊ 0⤋

D 6 is correct.

(x+y)/(xy)=4
xy=3
Therefore

x+y=12

average of x and y is
(x+y)/2
=12/2
=6

2007-04-10 23:43:13 · answer #4 · answered by iyiogrenci 6 · 1⤊ 0⤋