In a shop, 4 pens and 5 files cost $17.70. Joseph bought 5 pens and 6 files at $21.60 from the book shop.
- Find the cost of 1 pen and 1 file.
- What was the cost of 1 file?
(a)
Let 1 pen be 1 P.
Let 1 file be 1 F.
4 P + 5 F = 17.70 --- (1)
5 P + 6 F = 21.60 --- (2)
(2) - (1)
1 P + 1 F = 21.60 --- 17.70
1 P + 1 F = 3.90 --- (3)
Cost of 1 pen and 1 file = $3.90
(b)
(3)
x4 4 P + 4 F = 15.60 --- (4)
(1) - (4)
1 F = 17.70 - 15.60 = $2.10
Cost of 1 file = $2.10
Answer(s): (a) $3.90; (b) $2.10