1 marble costs $7.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 33 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 7 - 5
= 70 - 5
= $65
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 7
= $21
Cost of 13 marbles
= 65 + 21
= $86
(c)
Number of sets of 10 marbles
= 33 ÷ 10
= 3 r 3
Cost of 30 marbles
= 3 x 65
= $195
Cost of 3 marbles
= 3 x 7
= $21
Cost of 33 marbles
= 195 + 21
= $216
Answer(s): (a) $65; (b) $86; (c) $216