1 marble costs $9.
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 22 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 9 - 3
= 90 - 3
= $87
(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
= 87 + 72
= $159
(c)
Number of sets of 10 marbles
= 22 ÷ 10
= 2 r 2
Cost of 20 marbles
= 2 x 87
= $174
Cost of 2 marbles
= 2 x 9
= $18
Cost of 22 marbles
= 174 + 18
= $192
Answer(s): (a) $87; (b) $159; (c) $192