1 marble costs $5.
For every 10 marbles bought, a discount of $5 is given.
- How much do 10 marbles cost?
- How much do 13 marbles cost?
- How much do 35 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 5 - 5
= 50 - 5
= $45
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 5
= $15
Cost of 13 marbles
= 45 + 15
= $60
(c)
Number of sets of 10 marbles
= 35 ÷ 10
= 3 r 5
Cost of 30 marbles
= 3 x 45
= $135
Cost of 5 marbles
= 5 x 5
= $25
Cost of 35 marbles
= 135 + 25
= $160
Answer(s): (a) $45; (b) $60; (c) $160