1 marble costs $3.
For every 10 marbles bought, a discount of $7 is given.
- How much do 10 marbles cost?
- How much do 17 marbles cost?
- How much do 34 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 3 - 7
= 30 - 7
= $23
(b)
Number of marbles that do not belong to a set
= 17 ÷ 10
= 1 r 7
Cost of the 7 extra marbles
= 7 x 3
= $21
Cost of 17 marbles
= 23 + 21
= $44
(c)
Number of sets of 10 marbles
= 34 ÷ 10
= 3 r 4
Cost of 30 marbles
= 3 x 23
= $69
Cost of 4 marbles
= 4 x 3
= $12
Cost of 34 marbles
= 69 + 12
= $81
Answer(s): (a) $23; (b) $44; (c) $81