If Adam buys 3 marbles and 4 beads, it costs $42.60.
If Adam buys 4 marbles and 3 beads, he will need another $0.90.
- 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 = 42.60 --- (1)
4 marbles + 3 beads = 42.60 + 0.90 = 43.50 --- (2)
(1) + (2)
7 marbles + 7 beads = 86.10 --- (3)
(3)
÷ 7 1 marble + 1 bead = 86.10 ÷ 7 = 12.30 --- (4)
Cost of 1 marble and 1 bead = $12.30
(b)
4 marbles + 3 beads = 43.50 --- (2)
(4)
x 3 3 marbles + 3 beads = 3 x 12.30 = 36.90 --- (5)
(2) - (5)
4 marbles + 3 beads - 3 marbles - 3 beads = 43.50 - 36.90
4 marbles - 3 marbles + 3 beads - 3 beads = 6.60
1 marble = 6.60
Cost of 1 marble = $6.60
(c)
Substitute 1 marble = 6.60 into (4).
1 marble + 1 bead = 12.30
6.60 + 1 bead = 12.30
1 bead = 12.30 - 6.60 = 5.70
Cost of 1 bead = $5.70
Answer(s): (a) $12.30; (b) $6.60; (c) $5.70