The ratio of the number of red stickers to blue stickers is 3 : 2.
After Adam gives away 75 red stickers and gives away 80 blue stickers,
the ratio becomes of the number of red stickers to blue stickers is 7 : 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 7 = (4) |
Before |
12 u |
3 u |
2 u |
14 u |
Change |
- 300 |
- 75 |
- 80 |
- 560 |
After |
28 p |
7 p |
4 p |
28 p |
3 u - 75 = 7 p --- (1)
2 u - 80 = 4 p --- (2)
Make p the same.
(1) x 4
12 u - 300 = 28 p --- (3)
(2) x 7
14 u - 560 = 28 p --- (4)
(4) = (3)
14 u - 560 = 12 u - 300
14 u - 12 u = 560 - 300
2 u = 260
1 u = 260 ÷ 2 = 130
Number of stickers that Adam has now
= 3 u - 75 + 2 u - 80
= 5 u - 155
= 5 x 130 - 155
= 650 - 155
= 495
Answer(s): 495