grandh01 wrote:1) At a certain theatre, the cost if each adult's ticket is $5 and the cost if each child's ticket is $2. What is the average cost of all the adults and children's tickets sold at the theatre yesterday?
1) Yesterday the ratio of the number of children's tickets sold at the theatre to the number of adults tickets sold at the theatre was 3 to 2.
2) Yesterday 80 adults tickets were sold at the theatre.
We are given each adult's ticket is $5 and each child's ticket is $2. We need to find the average cost of tickets sold.
Let number of tickets sold to adults be a and to children be c.
Then the average Ave=(5a+2c)/(a+c)
With this in mind, let's look at the statements.
1) Yesterday the ratio of the number of children's tickets sold at the theatre to the number of adults tickets sold at the theatre was 3 to 2.
We are told that c/a=3/2. Hence c=3/2a. If we substitute this value of c in our Ave. eqn, we can find the answer. Sufficient.
2) Yesterday 80 adults tickets were sold at the theatre.
This doesn't tell us how many childrens or adult tickets were sold. Too many ratios. Insufficient.
Answer is hence
A
Alternate way:
We need to find the average of 2 items. By method of balancing (allegation), we need only the ratio between the quantities of the two to find the average. With this in mind.
1. Tells us the ratio. Sufficient.
2. Doesn't tell us about the ratio. Insufficient. (
Mind you if there were different numbers such as 30 for one child's ticket and 50 for each adult's, this equation would have been sufficient).
Hence still A is correct for this question.
Let me know if this helps 
