1 marble costs $9.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 18 marbles cost?
- How much do 35 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 9 - 5
= 90 - 5
= $85
(b)
Number of marbles that do not belong to a set
= 18 ÷ 10
= 1 r 8
Cost of the 8 extra marbles
= 8 x 9
= $72
Cost of 18 marbles
= 85 + 72
= $157
(c)
Number of sets of 10 marbles
= 35 ÷ 10
= 3 r 5
Cost of 30 marbles
= 3 x 85
= $255
Cost of 5 marbles
= 5 x 9
= $45
Cost of 35 marbles
= 255 + 45
= $300
Answer(s): (a) $85; (b) $157; (c) $300