1 marble costs $3.
For every 10 marbles bought, a discount of $7 is given.
- How much do 10 marbles cost?
- How much do 16 marbles cost?
- How much do 33 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
= 16 ÷ 10
= 1 r 6
Cost of the 6 extra marbles
= 6 x 3
= $18
Cost of 16 marbles
= 23 + 18
= $41
(c)
Number of sets of 10 marbles
= 33 ÷ 10
= 3 r 3
Cost of 30 marbles
= 3 x 23
= $69
Cost of 3 marbles
= 3 x 3
= $9
Cost of 33 marbles
= 69 + 9
= $78
Answer(s): (a) $23; (b) $41; (c) $78