1 marble costs $9.
For every 10 marbles bought, a discount of $7 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 9 - 7
= 90 - 7
= $83
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 9
= $27
Cost of 13 marbles
= 83 + 27
= $110
(c)
Number of sets of 10 marbles
= 25 ÷ 10
= 2 r 5
Cost of 20 marbles
= 2 x 83
= $166
Cost of 5 marbles
= 5 x 9
= $45
Cost of 25 marbles
= 166 + 45
= $211
Answer(s): (a) $83; (b) $110; (c) $211