1 marble costs $4.
For every 10 marbles bought, a discount of $3 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 37 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 4 - 3
= 40 - 3
= $37
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 4
= $12
Cost of 13 marbles
= 37 + 12
= $49
(c)
Number of sets of 10 marbles
= 37 ÷ 10
= 3 r 7
Cost of 30 marbles
= 3 x 37
= $111
Cost of 7 marbles
= 7 x 4
= $28
Cost of 37 marbles
= 111 + 28
= $139
Answer(s): (a) $37; (b) $49; (c) $139