1 marble costs $7.
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 36 marbles cost?
(a)
Cost of every 10 marbles
= 10 x 7 - 7
= 70 - 7
= $63
(b)
Number of marbles that do not belong to a set
= 13 ÷ 10
= 1 r 3
Cost of the 3 extra marbles
= 3 x 7
= $21
Cost of 13 marbles
= 63 + 21
= $84
(c)
Number of sets of 10 marbles
= 36 ÷ 10
= 3 r 6
Cost of 30 marbles
= 3 x 63
= $189
Cost of 6 marbles
= 6 x 7
= $42
Cost of 36 marbles
= 189 + 42
= $231
Answer(s): (a) $63; (b) $84; (c) $231