Adam spends $13.80 on 3 marbles and 4 beads.
A marble costs $2.50 more than 1 bead.
- How much does 1 marble cost?
- How much do 7 marbles cost?
- How much do a bead and 7 marbles cost?
- How much do 7 marbles cost more than 1 bead?
(a)
Let the cheaper item be 1 u.
Cost of 1 bead = 1 u
Cost of 1 marble = 1 u + 2.50
Total cost of 3 marbles and 4 beads
= 3(1 u + 2.50) + 4 u
= 3 u + 7.50 + 4 u
= 3 u + 4 u + 7.50
= 7 u + 7.50
7 u + 7.50 = 13.80
7 u = 13.80 - 7.50
7 u = 6.30
1 u = 6.30 ÷ 7 = 0.90
Cost of 1 marble
= 1 u + 2.50
= 0.90 + 2.50
= $3.40
(b)
Cost of 7 marbles
= 7 x 3.40
= $23.80
(c)
Cost of 1 bead and 7 marbles
= 0.90 + 23.80
= $24.70
(d)
Cost of 7 marbles more than 1 bead
= 23.80 - 0.90
= $22.90
Answer(s): (a) $3.40; (b) $23.80; (c) $24.70; (d) $22.90