The number of purple files is thrice the number of orange files. The number of orange files is 7 more than the number of brown files. The total number of files is 133. The cost of each purple file is $3.20 and the cost of each brown file is $2.40. The total cost of all the files is $355.60.
- Find the number of brown files.
- Find the cost of a orange file.
(a)
Number of brown files = 1 u
Number of orange files = 1 u + 7
Number of purple files
= 3(1 u + 7)
= 3 u + 21
Total of number of files
= 1 u + 1 u + 7 + 3 u + 21
= 5 u + 28
5 u + 28 = 133
5 u = 133 - 28
5 u = 105
1 u = 105 ÷ 5 = 21
Number of brown files
= 1 u
= 21
(b)
Number of brown files = 21
Number of orange files
= 21 + 7
= 28
Number of purple files
= 3 x 28
= 84
Cost of brown files
= 21 x 2.40
= $50.40
Cost of purple files
= 84 x 3.20
= $268.80
Cost of orange files
= 355.60 - 268.80 - 50.40
= $36.40
Cost of 1 orange file
= 36.40 ÷ 28
= $1.30
Answer(s) (a) 21; (b) $1.30
