The ratio of the number of blue stickers to red stickers is 4 : 1.
After Adam buys another 42 red stickers and gives away 21 blue stickers,
the ratio becomes of the number of blue stickers to red stickers is 7 : 4.
How many stickers does Adam have now?
|
Make p the same (1) x 4 = (3) |
(1) Blue |
(2) Red |
Make p the same (2) x 7 = (4) |
Before |
16 u |
4 u |
1 u |
7 u |
Change |
- 84 |
- 21 |
+ 42 |
+ 294 |
After |
28 p |
7 p |
4 p |
28 p |
4 u + 42 = 7 p --- (1)
1 u - 21 = 4 p --- (2)
Make p the same.
(1)
x 416 u - 84 = 28 p --- (3)
(2)
x 77 u + 294 = 28 p --- (4)
(3) = (4)
16 u - 84 = 7 u + 294
16 u - 7 u = 84 + 294
9 u = 378
1 u = 378 ÷ 9 = 42
Number of stickers that Adam have now
= 4 u + 42 + 1 u - 21
= 4 u + 1 u + 42 - 21
= 5 u + 21
= 5 x 42 + 21
= 210 + 21
= 231
Answer(s): 231