1 marble costs $9.
For every 10 marbles bought, a discount of $4 is given.
- How much do 10 marbles cost?
- How much do 17 marbles cost?
- How much do 22 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
= 17 ÷ 10
= 1 r 7
Cost of the 7 extra marbles
= 7 x 9
= $63
Cost of 17 marbles
= 86 + 63
= $149
(c)
Number of sets of 10 marbles
= 22 ÷ 10
= 2 r 2
Cost of 20 marbles
= 2 x 86
= $172
Cost of 2 marbles
= 2 x 9
= $18
Cost of 22 marbles
= 172 + 18
= $190
Answer(s): (a) $86; (b) $149; (c) $190