If Adam buys 4 marbles and 5 beads, it costs $51.70.
If Adam buys 5 marbles and 4 beads, he will need another $3.70.
- Find the cost of 1 marble and 1 bead.
- Find the cost of 1 marble.
- Find the cost of 1 bead.
(a)
4 marbles + 5 beads = 51.70 --- (1)
5 marbles + 4 beads = 51.70 + 3.70 = 55.40 --- (2)
(1) + (2)
9 marbles + 9 beads = 107.10 --- (3)
(3)
÷ 9 1 marble + 1 bead = 107.10 ÷ 9 = 11.90 --- (4)
Cost of 1 marble and 1 bead = $11.90
(b)
5 marbles + 4 beads = 55.40 --- (2)
(4)
x 4 4 marbles + 4 beads = 4 x 11.90 = 47.60 --- (5)
(2) - (5)
5 marbles + 4 beads - 4 marbles - 4 beads = 55.40 - 47.60
5 marbles - 4 marbles + 4 beads - 4 beads = 7.80
1 marble = 7.80
Cost of 1 marble = $7.80
(c)
Substitute 1 marble = 7.80 into (4).
1 marble + 1 bead = 11.90
7.80 + 1 bead = 11.90
1 bead = 11.90 - 7.80 = 4.10
Cost of 1 bead = $4.10
Answer(s): (a) $11.90; (b) $7.80; (c) $4.10