1 marble costs $7.
For every 10 marbles bought, a discount of $4 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 25 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 7 - 4
= 70 - 4
= $66
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 7
= $21
Cost of 13 marbles
= 66 + 21
= $87
(c)
Number of sets of 10 marbles
= 25 ÷ 10
= 2 r 5
Cost of 20 marbles
= 2 x 66
= $132
Cost of 5 marbles
= 5 x 7
= $35
Cost of 25 marbles
= 132 + 35
= $167
Answer(s): (a) $66; (b) $87; (c) $167