Some stickers are packed into exactly packets of 7.
If the stickers are repacked into packets of 13,
there are 2 less packets and needs 5 more stickers to make another packet.
- How many packets are there?
- How many stickers are there?
|
Packets of 7 |
Packets of 13 |
Number |
1 u |
1 u - 2 |
Value |
7 |
13 |
Total value |
7 u |
13 u - 18 |
(a)
Let the number of packets of 7 be 1 u.
Number of stickers if they are in packets of 7
= 1 u x 7
= 7 u
Number of stickers left if another packet is not packed
= 13 - 5
= 8
Number of stickers if they are in packets of 13
= 13(1 u - 2) + 8
= 13 u - 26 + 8
= 13 u - 18
7 u = 13 u - 18
13 u - 7 u = 18
6 u = 18
1 u = 18 ÷ 6 = 3
Number of packets of 7
= 1 u
= 3
(b)
Number of stickers
= 7 u
= 7 x 3
= 21
Answer(s): (a) 3; (b) 21