1 marble costs $7.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 12 marbles cost?
- How much do 25 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
= 12 ÷ 10
= 1 r 2
Cost of the 2 extra marbles
= 2 x 7
= $14
Cost of 12 marbles
= 67 + 14
= $81
(c)
Number of sets of 10 marbles
= 25 ÷ 10
= 2 r 5
Cost of 20 marbles
= 2 x 67
= $134
Cost of 5 marbles
= 5 x 7
= $35
Cost of 25 marbles
= 134 + 35
= $169
Answer(s): (a) $67; (b) $81; (c) $169