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 29 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
= 29 ÷ 10
= 2 r 9
Cost of 20 marbles
= 2 x 65
= $130
Cost of 9 marbles
= 9 x 7
= $63
Cost of 29 marbles
= 130 + 63
= $193
Answer(s): (a) $65; (b) $86; (c) $193