2 beads and 1 marble cost $11.80.
1 bead and 2 marbles cost $12.80.
- Find the cost of 1 bead and 1 marble.
- Find the cost of 1 marble.
- Find the cost of 1 bead.
- Find the cost of 9 beads and 9 marbles.
(a)
2 beads + 1 marble = 11.80 --- (1)
1 bead + 2 marbles = 12.80 --- (2)
(1) + (2)
3 beads + 3 marbles = 11.80 + 12.80
3 beads + 3 marbles = 24.60 --- (3)
(3)
÷ 3
3 beads + 3 marbles = 24.60
1 bead + 1 marble = 24.60 ÷ 3
1 bead + 1 marble = 8.20 --- (4)
Cost of 1 bead and 1 marble = $8.20
(b)
(2) - (4)
(1 bead + 2 marbles) - (1 bead + 1 marble) = 12.80 - 8.20
1 bead - 1 bead + 2 marbles - 1 marble = 4.60
1 marble = 4.60
Cost of 1 marble = $4.60
(c)
Substitute 1 marble = 4.60 into (4).
1 bead + 1 marble = 8.20
1 bead + 4.60 = 8.20
1 bead = 8.20 - 4.60 = 3.60
Cost of 1 bead = $3.60
(d)
(4)
x 9 1 bead + 1 marble = 8.20
9 x (1 bead + 1 marble) = 9 x 8.20
9 beads + 9 marbles = 73.80
Cost of 9 beads and 9 marbles = $73.80
Answer(s): (a) $8.20; (b) $4.60; (c) $3.60; (d) $73.80