Adam buys a bead for $9.
He also buys a marble.
The bead costs 3 times as much as the marble.
- How much less does the marble cost than the bead?
- How much does he spend altogether?
- How much are 7 marbles?
- What is the difference in cost between 4 beads and 5 marbles?
(a)
Choose the cheaper item to be 1 u.
The bead costs 3 times as much as the marble.
The marble is cheaper.
Cost of the marble = 1 u
Cost of the bead = 3 u = $9
3 u = 9
1 u = 9 ÷ 3 = 3
Amount that the marble costs less than the bead
= 3 u - 1 u
= 2 u
= 2 x 3
= $6
(b)
Total amount that Adam spends
= 1 u + 3 u
= 4 u
= 4 x 3
= $12
(c)
Cost of 7 marbles
= 7 x 1 u
= 7 u
= 7 x 3
= $21
(d )
Difference in the cost between 6 beads and 5 marbles
= (4 x 3 u) - (5 x 1 u)
= 12 u - 5 u
= 7 u
= 7 x 3
= $21
Answer(s): (a) $6; (b) $12; (c) $21; (d) $21