1 marble costs $5.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 14 marbles cost?
- How much do 21 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 5 - 3
= 50 - 3
= $47
(b)
Number of marbles that do not belong to a set
= 14 ÷ 10
= 1 r 4
Cost of the 4 extra marbles
= 4 x 5
= $20
Cost of 14 marbles
= 47 + 20
= $67
(c)
Number of sets of 10 marbles
= 21 ÷ 10
= 2 r 1
Cost of 20 marbles
= 2 x 47
= $94
Cost of 1 marbles
= 1 x 5
= $5
Cost of 21 marbles
= 94 + 5
= $99
Answer(s): (a) $47; (b) $67; (c) $99