A school has only two classes - class X and class Y.
Students in class X each have two pencils and one pen, and students in class Y each have one pencil and three pens. The average number of peicils each student has is 1.6.
What is the average number of pens each student has?
Student in class X - 2 pencils, 1 pen
Student in class Y - 1 pencil , 3 pens
No. of students in class X = x
No. of students in class Y = y
(2x+y)/(x+y) = 1.6
2x+y = 1.6x + 1.6y
.4x = .6y
x/y = 3/2
Since we know the ratio, we know the proportion.
(1(3) + 3 (2))/(3+2) = 9/5 = 1.8
Avg. no. of pens = 1.8
By the way, gamgatang, thanks for posting these questions, they are very helpful in my prep.