If Adam buys 3 beads and 4 marbles, it costs $39.70.
If Adam buys 4 beads and 3 marbles, he will need another $3.20.
- Find the cost of 1 bead and 1 marble.
- Find the cost of 1 bead.
- Find the cost of 1 marble.
(a)
3 beads + 4 marbles = 39.70 --- (1)
4 beads + 3 marbles = 39.70 + 3.20 = 42.90 --- (2)
(1) + (2)
7 beads + 7 marbles = 82.60 --- (3)
(3)
÷ 7 1 bead + 1 marble = 82.60 ÷ 7 = 11.80 --- (4)
Cost of 1 bead and 1 marble = $11.80
(b)
4 beads + 3 marbles = 42.90 --- (2)
(4)
x 3 3 beads + 3 marbles = 3 x 11.80 = 35.40 --- (5)
(2) - (5)
4 beads + 3 marbles - 3 beads - 3 marbles = 42.90 - 35.40
4 beads - 3 beads + 3 marbles - 3 marbles = 7.50
1 bead = 7.50
Cost of 1 bead = $7.50
(c)
Substitute 1 bead = 7.50 into (4).
1 bead + 1 marble = 11.80
7.50 + 1 marble = 11.80
1 marble = 11.80 - 7.50 = 4.30
Cost of 1 marble = $4.30
Answer(s): (a) $11.80; (b) $7.50; (c) $4.30