1 marble costs $9.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 22 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
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 9
= $27
Cost of 13 marbles
= 85 + 27
= $112
(c)
Number of sets of 10 marbles
= 22 ÷ 10
= 2 r 2
Cost of 20 marbles
= 2 x 85
= $170
Cost of 2 marbles
= 2 x 9
= $18
Cost of 22 marbles
= 170 + 18
= $188
Answer(s): (a) $85; (b) $112; (c) $188