2 beads and 1 marble cost $12.20.
1 bead and 2 marbles cost $13.30.
- 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 = 12.20 --- (1)
1 bead + 2 marbles = 13.30 --- (2)
(1) + (2)
3 beads + 3 marbles = 12.20 + 13.30
3 beads + 3 marbles = 25.50 --- (3)
(3)
÷ 3
3 beads + 3 marbles = 25.50
1 bead + 1 marble = 25.50 ÷ 3
1 bead + 1 marble = 8.50 --- (4)
Cost of 1 bead and 1 marble = $8.50
(b)
(2) - (4)
(1 bead + 2 marbles) - (1 bead + 1 marble) = 13.30 - 8.50
1 bead - 1 bead + 2 marbles - 1 marble = 4.80
1 marble = 4.80
Cost of 1 marble = $4.80
(c)
Substitute 1 marble = 4.80 into (4).
1 bead + 1 marble = 8.50
1 bead + 4.80 = 8.50
1 bead = 8.50 - 4.80 = 3.70
Cost of 1 bead = $3.70
(d)
(4)
x 9 1 bead + 1 marble = 8.50
9 x (1 bead + 1 marble) = 9 x 8.50
9 beads + 9 marbles = 76.50
Cost of 9 beads and 9 marbles = $76.50
Answer(s): (a) $8.50; (b) $4.80; (c) $3.70; (d) $76.50