1 marble costs $3.
For every 10 marbles bought, a discount of $7 is given.
- How much do 10 marbles cost?
- How much do 15 marbles cost?
- How much do 27 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 3 - 7
= 30 - 7
= $23
(b)
Number of marbles that do not belong to a set
= 15 ÷ 10
= 1 r 5
Cost of the 5 extra marbles
= 5 x 3
= $15
Cost of 15 marbles
= 23 + 15
= $38
(c)
Number of sets of 10 marbles
= 27 ÷ 10
= 2 r 7
Cost of 20 marbles
= 2 x 23
= $46
Cost of 7 marbles
= 7 x 3
= $21
Cost of 27 marbles
= 46 + 21
= $67
Answer(s): (a) $23; (b) $38; (c) $67