The ratio of the number of red stickers to blue stickers is 5 : 2.
After Adam buys another 42 blue stickers and gives away 40 red 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 |
20 u |
5 u |
2 u |
10 u |
Change |
- 160 |
- 40 |
+ 42 |
+ 210 |
After |
20 p |
5 p |
4 p |
20 p |
5 u + 42 = 5 p --- (1)
2 u - 40 = 4 p --- (2)
Make p the same.
(1)
x 420 u - 160 = 20 p --- (3)
(2)
x 510 u + 210 = 20 p --- (4)
(3) = (4)
20 u - 160 = 10 u + 210
20 u - 10 u = 160 + 210
10 u = 370
1 u = 370 ÷ 10 = 37
Number of stickers that Adam have now
= 5 u + 42 + 2 u - 40
= 5 u + 2 u + 42 - 40
= 7 u + 2
= 7 x 37 + 2
= 259 + 2
= 261
Answer(s): 261