1 marble costs $7.
For every 10 marbles bought, a discount of $6 is given.
- How much do 10 marbles cost?
- How much do 16 marbles cost?
- How much do 23 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 7 - 6
= 70 - 6
= $64
(b)
Number of marbles that do not belong to a set
= 16 ÷ 10
= 1 r 6
Cost of the 6 extra marbles
= 6 x 7
= $42
Cost of 16 marbles
= 64 + 42
= $106
(c)
Number of sets of 10 marbles
= 23 ÷ 10
= 2 r 3
Cost of 20 marbles
= 2 x 64
= $128
Cost of 3 marbles
= 3 x 7
= $21
Cost of 23 marbles
= 128 + 21
= $149
Answer(s): (a) $64; (b) $106; (c) $149