1 marble costs $8.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 15 marbles cost?
- How much do 28 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 8 - 3
= 80 - 3
= $77
(b)
Number of marbles that do not belong to a set
= 15 ÷ 10
= 1 r 5
Cost of the 5 extra marbles
= 5 x 8
= $40
Cost of 15 marbles
= 77 + 40
= $117
(c)
Number of sets of 10 marbles
= 28 ÷ 10
= 2 r 8
Cost of 20 marbles
= 2 x 77
= $154
Cost of 8 marbles
= 8 x 8
= $64
Cost of 28 marbles
= 154 + 64
= $218
Answer(s): (a) $77; (b) $117; (c) $218