1 marble costs $4.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 15 marbles cost?
- How much do 23 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 4 - 5
= 40 - 5
= $35
(b)
Number of marbles that do not belong to a set
= 15 ÷ 10
= 1 r 5
Cost of the 5 extra marbles
= 5 x 4
= $20
Cost of 15 marbles
= 35 + 20
= $55
(c)
Number of sets of 10 marbles
= 23 ÷ 10
= 2 r 3
Cost of 20 marbles
= 2 x 35
= $70
Cost of 3 marbles
= 3 x 4
= $12
Cost of 23 marbles
= 70 + 12
= $82
Answer(s): (a) $35; (b) $55; (c) $82