1 marble costs $4.
For every 10 marbles bought, a discount of $4 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 4 - 4
= 40 - 4
= $36
(b)
Number of marbles that do not belong to a set
= 15 ÷ 10
= 1 r 5
Cost of the 5 extra marbles
= 5 x 4
= $20
Cost of 15 marbles
= 36 + 20
= $56
(c)
Number of sets of 10 marbles
= 28 ÷ 10
= 2 r 8
Cost of 20 marbles
= 2 x 36
= $72
Cost of 8 marbles
= 8 x 4
= $32
Cost of 28 marbles
= 72 + 32
= $104
Answer(s): (a) $36; (b) $56; (c) $104