1 marble costs $6.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 12 marbles cost?
- How much do 39 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 6 - 5
= 60 - 5
= $55
(b)
Number of marbles that do not belong to a set
= 12 ÷ 10
= 1 r 2
Cost of the 2 extra marbles
= 2 x 6
= $12
Cost of 12 marbles
= 55 + 12
= $67
(c)
Number of sets of 10 marbles
= 39 ÷ 10
= 3 r 9
Cost of 30 marbles
= 3 x 55
= $165
Cost of 9 marbles
= 9 x 6
= $54
Cost of 39 marbles
= 165 + 54
= $219
Answer(s): (a) $55; (b) $67; (c) $219