The ratio of the number of red stickers to green stickers is 3 : 2.
After Adam buys another 20 red stickers and 70 green stickers,
the ratio becomes of the number of red stickers to green stickers is 8 : 7.
How many stickers does Adam have now?
|
Make p the same (1) x 7 = (3) |
(1) Red |
(2) Green |
Make p the same (2) x 8 = (4) |
Before |
21 u |
3 u |
2 u |
16 u |
Change |
+ 140 |
+ 20 |
+ 70 |
+ 560 |
After |
21 u + 140 |
3 u + 20 |
2 u + 70 |
16 u + 560 |
Comparing the red stickers and the green stickers in the end |
56 p |
8 p |
7 p |
56 p |
3 u + 20 = 8 p --- (1)
2 u + 70 = 7 p --- (2)
Make p the same by using the LCM of 7 and 8.
LCM of 7 and 8 is 56.
(1)
x 7 21 u + 140 = 56 p --- (3)
(2)
x 8 16 u + 560 = 56 p --- (4)
(3) = (4)
21 u + 140 = 16 u + 560
21 u - 16 u = 560 - 140
5 u = 420
1 u = 420 ÷ 5 = 84
Number of stickers that Adam has now
= 3 u + 20 + 2 u + 70
= 3 u + 2 u + 20 + 70
= 5 u + 90
= 5 x 84 + 90
= 420 + 90
= 510
Answer(s): 510