A bookshop was selling textbooks and workbooks. A textbook cost 3/5 more than a workbook. 35% of the books sold were textbooks. If the price of a workbook was $6, and $108 more was collected from the sales of workbooks than textbooks, how many books were sold altogether?
Let the number of textbooks = T
And let the number of workbooks = W
If the price of a workbook was $6, then the price of a textbook = $6 ( 1 + 3/5) = $6 ( 8/5) = $9.60
35% of the books sold were textbooks so 65% were workbooks
Let the total number of books sold = S
So.....the textbooks = .35S and the workbooks = .65S
Putting all of this together......
Number of workbooks sold * cost each - Number of textbooks sold * cost each = $108
.65S(6) - .35S ( 9.6) = 108 simplify
3.90S - 3.36S = 108
.54S = 108
108 / .54 = S = 200 books total
Price of Workbook = $6
Price of Textbook = (3/5)(6) + 6 = $9.6
Let T = number of Textbooks
W = number of Workbooks
S = total number of textbooks and workbooks
S = T + W --> equation (1)
* 0.35S = T --> equation (2)
* 6W = 108 + 9.6T --> equation (3)
equation (2) in equation (1)
S = T + W
S = 0.35S + W
0.65S = W --> equation (4)
Total sales:
6W + 9.6T = (108 + 9.6T) + 9.6T
6W = 108 + 9.6T
* T = 0.35 (equation (2))
6W = 108 + 9.6 (0.35S)
6W/6 = (108 + 3.36S)/6
W = 18 + 0.56S --> equation (5)
equation (4) = equation (5)
0.65S = 18 + 0.56S
0.65S - 0.56 S = 18
0.09S/0.09 = 18/0.09
S = 200 books
200 books was sold altogether