In a stationery shop, 3 pens and 4 notebooks cost $16.80. Joseph bought 4 pens and 5 notebooks at $21.90 from the book shop.
- Find the cost of 1 pen and 1 notebook.
- What was the cost of 1 notebook?
(a)
Let 1 pen be 1 P.
Let 1 notebook be 1 N.
3 P + 4 N = 16.80 --- (1)
4 P + 5 N = 21.90 --- (2)
(2) - (1)
1 P + 1 N = 21.90 --- 16.80
1 P + 1 N = 5.10 --- (3)
Cost of 1 pen and 1 notebook = $5.10
(b)
(3)
x3 3 P + 3 N = 15.30 --- (4)
(1) - (4)
1 N = 16.80 - 15.30 = $1.50
Cost of 1 notebook = $1.50
Answer(s): (a) $5.10; (b) $1.50