1 marble costs $5.
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 25 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 5 - 5
= 50 - 5
= $45
(b)
Number of marbles that do not belong to a set
= 18 ÷ 10
= 1 r 8
Cost of the 8 extra marbles
= 8 x 5
= $40
Cost of 18 marbles
= 45 + 40
= $85
(c)
Number of sets of 10 marbles
= 25 ÷ 10
= 2 r 5
Cost of 20 marbles
= 2 x 45
= $90
Cost of 5 marbles
= 5 x 5
= $25
Cost of 25 marbles
= 90 + 25
= $115
Answer(s): (a) $45; (b) $85; (c) $115