2 beads and 1 marble cost $9.30.
1 bead and 2 marbles cost $10.80.
- 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 4 beads and 4 marbles.
(a)
2 beads + 1 marble = 9.30 --- (1)
1 bead + 2 marbles = 10.80 --- (2)
(1) + (2)
3 beads + 3 marbles = 9.30 + 10.80
3 beads + 3 marbles = 20.10 --- (3)
(3)
÷ 3
3 beads + 3 marbles = 20.10
1 bead + 1 marble = 20.10 ÷ 3
1 bead + 1 marble = 6.70 --- (4)
Cost of 1 bead and 1 marble = $6.70
(b)
(2) - (4)
(1 bead + 2 marbles) - (1 bead + 1 marble) = 10.80 - 6.70
1 bead - 1 bead + 2 marbles - 1 marble = 4.10
1 marble = 4.10
Cost of 1 marble = $4.10
(c)
Substitute 1 marble = 4.10 into (4).
1 bead + 1 marble = 6.70
1 bead + 4.10 = 6.70
1 bead = 6.70 - 4.10 = 2.60
Cost of 1 bead = $2.60
(d)
(4)
x 4 1 bead + 1 marble = 6.70
4 x (1 bead + 1 marble) = 4 x 6.70
4 beads + 4 marbles = 26.80
Cost of 4 beads and 4 marbles = $26.80
Answer(s): (a) $6.70; (b) $4.10; (c) $2.60; (d) $26.80