Adam has some red stickers and blue stickers.
If 315 red stickers are removed, 90% of the stickers will be blue stickers.
If 85 red stickers are added, 30% of the stickers will be blue stickers.
- How many red stickers are there?
- How many blue stickers are there?
|
Scenario 1 |
Scenario 2 |
|
Red |
Blue |
Red |
Blue |
Before |
1 u + 315 |
9 u |
21 u - 85 |
9 u |
Change |
- 315 |
No change |
+ 85 |
No change |
After |
1x1 = 1 u |
9x1 = 9 u |
7x3 = 21 u |
3x3 = 9 u |
(a)
90% =
90100 =
91030% =
30100 =
310Scenario 1 Fraction of the stickers that are red in the end
= 1 -
910 =
110 Scenario 2
Fraction of the stickers that are red in the end
= 1 -
310 =
710 The number of blue stickers remains unchanged in both scenarios.
LCM of 9 and 3 = 9
21 u - 85 = 1 u + 315
21 u - 1 u = 315 + 85
20 u = 400
1 u = 400 ÷ 20 = 20
Number of red stickers
= 1 u + 315
= 1 x 20 + 315
= 20 + 315
= 335
(b)
Number of blue stickers
= 9 u
= 9 x 20
= 180
Answer(s): (a) 335; (b) 180