The ratio of the number of red stickers to green stickers is 3 : 1.
After Adam buys another 20 red stickers and 30 green stickers,
the ratio becomes of the number of red stickers to green stickers is 7 : 3.
How many stickers does Adam have now?
|
Make p the same (1) x 3 = (3) |
(1) Red |
(2) Green |
Make p the same (2) x 7 = (4) |
Before |
9 u |
3 u |
1 u |
7 u |
Change |
+ 60 |
+ 20 |
+ 30 |
+ 210 |
After |
9 u + 60 |
3 u + 20 |
1 u + 30 |
7 u + 210 |
Comparing the red stickers and the green stickers in the end |
21 p |
7 p |
3 p |
21 p |
3 u + 20 = 7 p --- (1)
1 u + 30 = 3 p --- (2)
Make p the same by using the LCM of 3 and 7.
LCM of 3 and 7 is 21.
(1)
x 3 9 u + 60 = 21 p --- (3)
(2)
x 7 7 u + 210 = 21 p --- (4)
(3) = (4)
9 u + 60 = 7 u + 210
9 u - 7 u = 210 - 60
2 u = 150
1 u = 150 ÷ 2 = 75
Number of stickers that Adam has now
= 3 u + 20 + 1 u + 30
= 3 u + 1 u + 20 + 30
= 4 u + 50
= 4 x 75 + 50
= 300 + 50
= 350
Answer(s): 350