1 marble costs $7.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 14 marbles cost?
- How much do 31 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
= 14 ÷ 10
= 1 r 4
Cost of the 4 extra marbles
= 4 x 7
= $28
Cost of 14 marbles
= 67 + 28
= $95
(c)
Number of sets of 10 marbles
= 31 ÷ 10
= 3 r 1
Cost of 30 marbles
= 3 x 67
= $201
Cost of 1 marbles
= 1 x 7
= $7
Cost of 31 marbles
= 201 + 7
= $208
Answer(s): (a) $67; (b) $95; (c) $208