In a shop, 3 notebooks and 4 files cost $19.70. Joseph bought 4 notebooks and 5 files at $25.20 from the book shop.
- Find the cost of 1 notebook and 1 file.
- What was the cost of 1 file?
(a)
Let 1 notebook be 1 N.
Let 1 file be 1 F.
3 N + 4 F = 19.70 --- (1)
4 N + 5 F = 25.20 --- (2)
(2) - (1)
1 N + 1 F = 25.20 --- 19.70
1 N + 1 F = 5.50 --- (3)
Cost of 1 notebook and 1 file = $5.50
(b)
(3)
x3 3 N + 3 F = 16.50 --- (4)
(1) - (4)
1 F = 19.70 - 16.50 = $3.20
Cost of 1 file = $3.20
Answer(s): (a) $5.50; (b) $3.20