A student bought 11 books for class. If the cost of his anatomy book was 3 times the mean cost of the other 10 books, then the cost of the anatomy book was what fraction of the total amount he paid for the 11 books?
Can anyone show me how to do this algebraically instead of plugging in numbers?

Question

A student bought 11 books for class. If the cost of his anatomy book was 3 times the mean cost of the other 10 books, then the cost of the anatomy book was what fraction of the total amount he paid for the 11 books?
Can anyone show me how to do this algebraically instead of plugging in numbers?

kropot72 · Answer

Let the mean cost of the other 10 books = m
Cost of anatomy book = 3m
Total amount paid for the 11 books = m + 3m = 4m

Can you finish it now?

anonymous · Answer

I apologize i forgot the answer choices. Maby this should make more sense: 
A) 2/13 B) 3/13 C) 3/11 D) 3/10 E) 10/13

anonymous · Answer

If I'm not wrong when I do it the way you explained i get 3/4

kropot72 · Answer

Sorry for my mistake. The total amount paid for the 11 books = 3m + 10m = 13m
Can you find the answer now?

anonymous · Answer

why is that 10m?

kropot72 · Answer

The average cost of each of the other 10 books = m
Therefore the total cost of the other 10 books is the average cost of each of the other 10 books multiplied by the number of books = m * 10 = 10m
Note that the anatomy book (the eleventh one) is not included in this part of the cost calculation.

kropot72 · Answer

The total amount paid for the 11 books = 3m + 10m = 13m
The amount paid for the anatomy book is 3m

anonymous · Answer

got it thanx :)

kropot72 · Answer

You're welcome :)