1 marble costs $7.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 18 marbles cost?
- How much do 38 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
= 18 ÷ 10
= 1 r 8
Cost of the 8 extra marbles
= 8 x 7
= $56
Cost of 18 marbles
= 67 + 56
= $123
(c)
Number of sets of 10 marbles
= 38 ÷ 10
= 3 r 8
Cost of 30 marbles
= 3 x 67
= $201
Cost of 8 marbles
= 8 x 7
= $56
Cost of 38 marbles
= 201 + 56
= $257
Answer(s): (a) $67; (b) $123; (c) $257