1 marble costs $6.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 19 marbles cost?
- How much do 25 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 6 - 3
= 60 - 3
= $57
(b)
Number of marbles that do not belong to a set
= 19 ÷ 10
= 1 r 9
Cost of the 9 extra marbles
= 9 x 6
= $54
Cost of 19 marbles
= 57 + 54
= $111
(c)
Number of sets of 10 marbles
= 25 ÷ 10
= 2 r 5
Cost of 20 marbles
= 2 x 57
= $114
Cost of 5 marbles
= 5 x 6
= $30
Cost of 25 marbles
= 114 + 30
= $144
Answer(s): (a) $57; (b) $111; (c) $144