1 marble costs $7.
For every 10 marbles bought, a discount of $4 is given.
- How much do 10 marbles cost?
- How much do 19 marbles cost?
- How much do 36 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
= 19 ÷ 10
= 1 r 9
Cost of the 9 extra marbles
= 9 x 7
= $63
Cost of 19 marbles
= 66 + 63
= $129
(c)
Number of sets of 10 marbles
= 36 ÷ 10
= 3 r 6
Cost of 30 marbles
= 3 x 66
= $198
Cost of 6 marbles
= 6 x 7
= $42
Cost of 36 marbles
= 198 + 42
= $240
Answer(s): (a) $66; (b) $129; (c) $240