1 marble costs $6.
For every 10 marbles bought, a discount of $7 is given.
- How much do 10 marbles cost?
- How much do 18 marbles cost?
- How much do 21 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 6 - 7
= 60 - 7
= $53
(b)
Number of marbles that do not belong to a set
= 18 ÷ 10
= 1 r 8
Cost of the 8 extra marbles
= 8 x 6
= $48
Cost of 18 marbles
= 53 + 48
= $101
(c)
Number of sets of 10 marbles
= 21 ÷ 10
= 2 r 1
Cost of 20 marbles
= 2 x 53
= $106
Cost of 1 marbles
= 1 x 6
= $6
Cost of 21 marbles
= 106 + 6
= $112
Answer(s): (a) $53; (b) $101; (c) $112