In a shop, 4 files and 5 pens cost $23.70. Joseph bought 5 files and 6 pens at $28.80 from the book shop.
- Find the cost of 1 file and 1 pen.
- What was the cost of 1 pen?
(a)
Let 1 file be 1 F.
Let 1 pen be 1 P.
4 F + 5 P = 23.70 --- (1)
5 F + 6 P = 28.80 --- (2)
(2) - (1)
1 F + 1 P = 28.80 --- 23.70
1 F + 1 P = 5.10 --- (3)
Cost of 1 file and 1 pen = $5.10
(b)
(3)
x4 4 F + 4 P = 20.40 --- (4)
(1) - (4)
1 P = 23.70 - 20.40 = $3.30
Cost of 1 pen = $3.30
Answer(s): (a) $5.10; (b) $3.30