1 marble costs $7.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 12 marbles cost?
- How much do 38 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 7 - 5
= 70 - 5
= $65
(b)
Number of marbles that do not belong to a set
= 12 ÷ 10
= 1 r 2
Cost of the 2 extra marbles
= 2 x 7
= $14
Cost of 12 marbles
= 65 + 14
= $79
(c)
Number of sets of 10 marbles
= 38 ÷ 10
= 3 r 8
Cost of 30 marbles
= 3 x 65
= $195
Cost of 8 marbles
= 8 x 7
= $56
Cost of 38 marbles
= 195 + 56
= $251
Answer(s): (a) $65; (b) $79; (c) $251