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 35 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
= 35 ÷ 10
= 3 r 5
Cost of 30 marbles
= 3 x 23
= $69
Cost of 5 marbles
= 5 x 3
= $15
Cost of 35 marbles
= 69 + 15
= $84
Answer(s): (a) $23; (b) $38; (c) $84