1 marble costs $6.
For every 10 marbles bought, a discount of $6 is given.
- How much do 10 marbles cost?
- How much do 15 marbles cost?
- How much do 31 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 6 - 6
= 60 - 6
= $54
(b)
Number of marbles that do not belong to a set
= 15 ÷ 10
= 1 r 5
Cost of the 5 extra marbles
= 5 x 6
= $30
Cost of 15 marbles
= 54 + 30
= $84
(c)
Number of sets of 10 marbles
= 31 ÷ 10
= 3 r 1
Cost of 30 marbles
= 3 x 54
= $162
Cost of 1 marbles
= 1 x 6
= $6
Cost of 31 marbles
= 162 + 6
= $168
Answer(s): (a) $54; (b) $84; (c) $168