The ratio of the number of red stickers to green stickers is 5 : 4.
After Adam buys another 20 red stickers and 40 green stickers,
the ratio becomes of the number of red stickers to green stickers is 7 : 6.
How many stickers does Adam have now?
|
Make p the same (1) x 6 = (3) |
(1) Red |
(2) Green |
Make p the same (2) x 7 = (4) |
Before |
30 u |
5 u |
4 u |
28 u |
Change |
+ 120 |
+ 20 |
+ 40 |
+ 280 |
After |
30 u + 120 |
5 u + 20 |
4 u + 40 |
28 u + 280 |
Comparing the red stickers and the green stickers in the end |
42 p |
7 p |
6 p |
42 p |
5 u + 20 = 7 p --- (1)
4 u + 40 = 6 p --- (2)
Make p the same by using the LCM of 6 and 7.
LCM of 6 and 7 is 42.
(1)
x 6 30 u + 120 = 42 p --- (3)
(2)
x 7 28 u + 280 = 42 p --- (4)
(3) = (4)
30 u + 120 = 28 u + 280
30 u - 28 u = 280 - 120
2 u = 160
1 u = 160 ÷ 2 = 80
Number of stickers that Adam has now
= 5 u + 20 + 4 u + 40
= 5 u + 4 u + 20 + 40
= 9 u + 60
= 9 x 80 + 60
= 720 + 60
= 780
Answer(s): 780