Some stickers are packed into exactly packets of 12.
If the stickers are repacked into packets of 9,
there are 7 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 + 7 |
Value |
12 |
9 |
Total value |
12 u |
9 u + 63 |
(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 + 7)
= 9 u + 63
9 u + 63 = 12 u
12 u - 9 u = 63
3 u = 63
1 u = 63 ÷ 3 = 21
Number of packets of 9
= 1 u + 7
= 21 + 7
= 28
(b)
Number of stickers
= 12 u
= 12 x 21
= 252
Answer(s): (a) 28; (b) 252