1 marble costs $7.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 16 marbles cost?
- How much do 29 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 7 - 3
= 70 - 3
= $67
(b)
Number of marbles that do not belong to a set
= 16 ÷ 10
= 1 r 6
Cost of the 6 extra marbles
= 6 x 7
= $42
Cost of 16 marbles
= 67 + 42
= $109
(c)
Number of sets of 10 marbles
= 29 ÷ 10
= 2 r 9
Cost of 20 marbles
= 2 x 67
= $134
Cost of 9 marbles
= 9 x 7
= $63
Cost of 29 marbles
= 134 + 63
= $197
Answer(s): (a) $67; (b) $109; (c) $197