3 marbles and 1 bead cost $4.90.
1 marble and 3 beads cost $5.90.
- Find the cost of 1 marble and 1 bead.
- Find the cost of 1 bead.
- Find the cost of 1 marble.
- Find the cost of 7 marbles and 7 beads.
(a)
3 marbles + 1 bead = 4.90 --- (1)
1 marble + 3 beads = 5.90 --- (2)
(1) + (2)
4 marbles + 4 beads = 4.90 + 5.90
4 marbles + 4 beads = 10.80 --- (3)
(3)
÷ 44 marbles + 4 beads = 10.80
1 marble + 1 bead = 10.80 ÷ 4
1 marble + 1 bead = 2.70 --- (4)
(b)
(2) - (4)
(1 marble + 3 beads) - (1 marble + 1 marble) = 5.90 - 2.70
1 marble - 1 marble + 3 beads - 1 bead = 3.20
2 beads = 3.20
1 bead = 3.20 ÷ 2 = 1.60
Cost of 1 bead = $1.60
(c)
Substitute 1 bead = 1.60 into (4).
1 marble + 1 bead = 2.70
1 marble + 1.60 = 2.70
1 marble = 2.70 - 1.60 = 1.10
Cost of 1 marble = $1.10
(d)
(4)
x 7 1 marble + 1 bead = 2.70
7 x (1 marble + 1 marble) = 7 x 2.70
7 marbles + 7 beads = 18.90
Cost of 7 marbles and 7 beads = $18.90
Answer(s): (a) $2.70; (b) $1.60; (c) $1.10; (d) $18.90