Some stickers are packed into exactly packets of 12.
If the stickers are repacked into packets of 9,
there are 5 more packets.
- How many packets of 9 are there?
- How many stickers are there?
|
Packets of 12 |
Packets of 9 |
Number |
1 u |
1 u + 5 |
Value |
12 |
9 |
Total value |
12 u |
9 u + 45 |
(a)
Let the number of packets of 12 be 1 u.
Number of stickers if they are in packets of 12
= 12 x 1 u
= 12 u
Number of stickers if they are in packets of 9
= 9 x (1 u + 5)
= 9 u + 45
9 u + 45 = 12 u
12 u - 9 u = 45
3 u = 45
1 u = 45 ÷ 3 = 15
Number of packets of 9
= 1 u + 5
= 15 + 5
= 20
(b)
Number of stickers
= 12 u
= 12 x 15
= 180
Answer(s): (a) 20; (b) 180