Some stickers are packed into exactly packets of 7.
If the stickers are repacked into packets of 20,
there are 4 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 20 |
Number |
1 u |
1 u - 4 |
Value |
7 |
20 |
Total value |
7 u |
20 u - 65 |
(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
= 20 - 5
= 15
Number of stickers if they are in packets of 20
= 20(1 u - 4) + 15
= 20 u - 80 + 15
= 20 u - 65
7 u = 20 u - 65
20 u - 7 u = 65
13 u = 65
1 u = 65 ÷ 13 = 5
Number of packets of 7
= 1 u
= 5
(b)
Number of stickers
= 7 u
= 7 x 5
= 35
Answer(s): (a) 5; (b) 35