1 marble costs $7.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 28 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
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 7
= $21
Cost of 13 marbles
= 67 + 21
= $88
(c)
Number of sets of 10 marbles
= 28 ÷ 10
= 2 r 8
Cost of 20 marbles
= 2 x 67
= $134
Cost of 8 marbles
= 8 x 7
= $56
Cost of 28 marbles
= 134 + 56
= $190
Answer(s): (a) $67; (b) $88; (c) $190