The number of green files is twice the number of blue files. The number of blue files is 7 more than the number of red files. The total number of files is 129. The cost of each green file is $4.20 and the cost of each red file is $1.50. The total cost of all the files is $397.50.
- Find the number of red files.
- Find the cost of a blue file.
(a)
Number of red files = 1 u
Number of blue files = 1 u + 7
Number of green files
= 2(1 u + 7)
= 2 u + 14
Total of number of files
= 1 u + 1 u + 7 + 2 u + 14
= 4 u + 21
4 u + 21 = 129
4 u = 129 - 21
4 u = 108
1 u = 108 ÷ 4 = 27
Number of red files
= 1 u
= 27
(b)
Number of red files = 27
Number of blue files
= 27 + 7
= 34
Number of green files
= 2 x 34
= 68
Cost of red files
= 27 x 1.50
= $40.50
Cost of green files
= 68 x 4.20
= $285.60
Cost of blue files
= 397.50 - 285.60 - 40.50
= $71.40
Cost of 1 blue file
= 71.40 ÷ 34
= $2.10
Answer(s) (a) 27; (b) $2.10
