The number of red files is thrice the number of green files. The number of green files is 8 more than the number of yellow files. The total number of files is 137. The cost of each red file is $3.90 and the cost of each yellow file is $2.70. The total cost of all the files is $448.20.
- Find the number of yellow files.
- Find the cost of a green file.
(a)
Number of yellow files = 1 u
Number of green files = 1 u + 8
Number of red files
= 3(1 u + 8)
= 3 u + 24
Total of number of files
= 1 u + 1 u + 8 + 3 u + 24
= 5 u + 32
5 u + 32 = 137
5 u = 137 - 32
5 u = 105
1 u = 105 ÷ 5 = 21
Number of yellow files
= 1 u
= 21
(b)
Number of yellow files = 21
Number of green files
= 21 + 8
= 29
Number of red files
= 3 x 29
= 87
Cost of yellow files
= 21 x 2.70
= $56.70
Cost of red files
= 87 x 3.90
= $339.30
Cost of green files
= 448.20 - 339.30 - 56.70
= $52.20
Cost of 1 green file
= 52.20 ÷ 29
= $1.80
Answer(s) (a) 21; (b) $1.80