1 marble costs $9.
For every 10 marbles bought, a discount of $6 is given.
- How much do 10 marbles cost?
- How much do 17 marbles cost?
- How much do 29 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 9 - 6
= 90 - 6
= $84
(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
= 84 + 63
= $147
(c)
Number of sets of 10 marbles
= 29 ÷ 10
= 2 r 9
Cost of 20 marbles
= 2 x 84
= $168
Cost of 9 marbles
= 9 x 9
= $81
Cost of 29 marbles
= 168 + 81
= $249
Answer(s): (a) $84; (b) $147; (c) $249