1 marble costs $9.
For every 10 marbles bought, a discount of $7 is given.
- How much do 10 marbles cost?
- How much do 14 marbles cost?
- How much do 39 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 9 - 7
= 90 - 7
= $83
(b)
Number of marbles that do not belong to a set
= 14 ÷ 10
= 1 r 4
Cost of the 4 extra marbles
= 4 x 9
= $36
Cost of 14 marbles
= 83 + 36
= $119
(c)
Number of sets of 10 marbles
= 39 ÷ 10
= 3 r 9
Cost of 30 marbles
= 3 x 83
= $249
Cost of 9 marbles
= 9 x 9
= $81
Cost of 39 marbles
= 249 + 81
= $330
Answer(s): (a) $83; (b) $119; (c) $330