1 marble costs $8.
For every 10 marbles bought, a discount of $7 is given.
- How much do 10 marbles cost?
- How much do 17 marbles cost?
- How much do 31 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 8 - 7
= 80 - 7
= $73
(b)
Number of marbles that do not belong to a set
= 17 ÷ 10
= 1 r 7
Cost of the 7 extra marbles
= 7 x 8
= $56
Cost of 17 marbles
= 73 + 56
= $129
(c)
Number of sets of 10 marbles
= 31 ÷ 10
= 3 r 1
Cost of 30 marbles
= 3 x 73
= $219
Cost of 1 marbles
= 1 x 8
= $8
Cost of 31 marbles
= 219 + 8
= $227
Answer(s): (a) $73; (b) $129; (c) $227