4 marbles and 1 bead cost $11.90.
1 marble and 4 beads cost $14.60.
- 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)
4 marbles + 1 bead = 11.90 --- (1)
1 marble + 4 beads = 14.60 --- (2)
(1) + (2)
5 marbles + 5 beads = 11.90 + 14.60
5 marbles + 5 beads = 26.50 --- (3)
(3)
÷ 55 marbles + 5 beads = 26.50
1 marble + 1 bead = 26.50 ÷ 5
1 marble + 1 bead = 5.30 --- (4)
(b)
(2) - (4)
(1 marble + 4 beads) - (1 marble + 1 marble) = 14.60 - 5.30
1 marble - 1 marble + 4 beads - 1 bead = 9.30
3 beads = 9.30
1 bead = 9.30 ÷ 3 = 3.10
Cost of 1 bead = $3.10
(c)
Substitute 1 bead = 3.10 into (4).
1 marble + 1 bead = 5.30
1 marble + 3.10 = 5.30
1 marble = 5.30 - 3.10 = 2.20
Cost of 1 marble = $2.20
(d)
(4)
x 7 1 marble + 1 bead = 5.30
7 x (1 marble + 1 marble) = 7 x 5.30
7 marbles + 7 beads = 37.10
Cost of 7 marbles and 7 beads = $37.10
Answer(s): (a) $5.30; (b) $3.10; (c) $2.20; (d) $37.10