1 marble costs $8.
For every 10 marbles bought, a discount of $6 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 21 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 8 - 6
= 80 - 6
= $74
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 8
= $24
Cost of 13 marbles
= 74 + 24
= $98
(c)
Number of sets of 10 marbles
= 21 ÷ 10
= 2 r 1
Cost of 20 marbles
= 2 x 74
= $148
Cost of 1 marbles
= 1 x 8
= $8
Cost of 21 marbles
= 148 + 8
= $156
Answer(s): (a) $74; (b) $98; (c) $156