If Adam buys 3 marbles and 4 beads, it costs $43.60.
If Adam buys 4 marbles and 3 beads, he will need another $1.70.
- Find the cost of 1 marble and 1 bead.
- Find the cost of 1 marble.
- Find the cost of 1 bead.
(a)
3 marbles + 4 beads = 43.60 --- (1)
4 marbles + 3 beads = 43.60 + 1.70 = 45.30 --- (2)
(1) + (2)
7 marbles + 7 beads = 88.90 --- (3)
(3)
÷ 7 1 marble + 1 bead = 88.90 ÷ 7 = 12.70 --- (4)
Cost of 1 marble and 1 bead = $12.70
(b)
4 marbles + 3 beads = 45.30 --- (2)
(4)
x 3 3 marbles + 3 beads = 3 x 12.70 = 38.10 --- (5)
(2) - (5)
4 marbles + 3 beads - 3 marbles - 3 beads = 45.30 - 38.10
4 marbles - 3 marbles + 3 beads - 3 beads = 7.20
1 marble = 7.20
Cost of 1 marble = $7.20
(c)
Substitute 1 marble = 7.20 into (4).
1 marble + 1 bead = 12.70
7.20 + 1 bead = 12.70
1 bead = 12.70 - 7.20 = 5.50
Cost of 1 bead = $5.50
Answer(s): (a) $12.70; (b) $7.20; (c) $5.50