The ratio of the number of red stickers to blue stickers is 7 : 5.
After Adam buys another 20 red stickers and 40 blue stickers,
the ratio becomes of the number of red stickers to blue stickers is 5 : 4.
How many stickers does Adam have now?
|
Make p the same (1) x 4 = (3) |
(1) Red |
(2) Blue |
Make p the same (2) x 5 = (4) |
Before |
28 u |
7 u |
5 u |
25 u |
Change |
+ 80 |
+ 20 |
+ 40 |
+ 200 |
After |
28 u + 80 |
7 u + 20 |
5 u + 40 |
25 u + 200 |
Comparing the red stickers and the blue stickers in the end |
20 p |
5 p |
4 p |
20 p |
7 u + 20 = 5 p --- (1)
5 u + 40 = 4 p --- (2)
Make p the same by using the LCM of 4 and 5.
LCM of 4 and 5 is 20.
(1)
x 4 28 u + 80 = 20 p --- (3)
(2)
x 5 25 u + 200 = 20 p --- (4)
(3) = (4)
28 u + 80 = 25 u + 200
28 u - 25 u = 200 - 80
3 u = 120
1 u = 120 ÷ 3 = 40
Number of stickers that Adam has now
= 7 u + 20 + 5 u + 40
= 7 u + 5 u + 20 + 40
= 12 u + 60
= 12 x 40 + 60
= 480 + 60
= 540
Answer(s): 540