The ratio of the number of red stickers to blue stickers is 5 : 2.
After Adam buys another 20 blue stickers and gives away 19 red stickers,
the ratio becomes of the number of red stickers to blue stickers is 9 : 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 9 = (4) |
Before |
20 u |
5 u |
2 u |
18 u |
Change |
- 76 |
- 19 |
+ 20 |
+ 180 |
After |
36 p |
9 p |
4 p |
36 p |
5 u + 20 = 9 p --- (1)
2 u - 19 = 4 p --- (2)
Make p the same.
(1)
x 420 u - 76 = 36 p --- (3)
(2)
x 918 u + 180 = 36 p --- (4)
(3) = (4)
20 u - 76 = 18 u + 180
20 u - 18 u = 76 + 180
2 u = 256
1 u = 256 ÷ 2 = 128
Number of stickers that Adam have now
= 5 u + 20 + 2 u - 19
= 5 u + 2 u + 20 - 19
= 7 u + 1
= 7 x 128 + 1
= 896 + 1
= 897
Answer(s): 897