1 marble costs $9.
For every 10 marbles bought, a discount of $4 is given.
- How much do 10 marbles cost?
- How much do 15 marbles cost?
- How much do 36 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 9 - 4
= 90 - 4
= $86
(b)
Number of marbles that do not belong to a set
= 15 ÷ 10
= 1 r 5
Cost of the 5 extra marbles
= 5 x 9
= $45
Cost of 15 marbles
= 86 + 45
= $131
(c)
Number of sets of 10 marbles
= 36 ÷ 10
= 3 r 6
Cost of 30 marbles
= 3 x 86
= $258
Cost of 6 marbles
= 6 x 9
= $54
Cost of 36 marbles
= 258 + 54
= $312
Answer(s): (a) $86; (b) $131; (c) $312