The ratio of the number of red stickers to blue stickers is 8 : 5.
After Adam buys another 20 red stickers and 70 blue stickers,
the ratio becomes of the number of red stickers to blue stickers is 7 : 5.
How many stickers does Adam have now?
|
Make p the same (1) x 5 = (3) |
(1) Red |
(2) Blue |
Make p the same (2) x 7 = (4) |
Before |
40 u |
8 u |
5 u |
35 u |
Change |
+ 100 |
+ 20 |
+ 70 |
+ 490 |
After |
40 u + 100 |
8 u + 20 |
5 u + 70 |
35 u + 490 |
Comparing the red stickers and the blue stickers in the end |
35 p |
7 p |
5 p |
35 p |
8 u + 20 = 7 p --- (1)
5 u + 70 = 5 p --- (2)
Make p the same by using the LCM of 5 and 7.
LCM of 5 and 7 is 35.
(1)
x 5 40 u + 100 = 35 p --- (3)
(2)
x 7 35 u + 490 = 35 p --- (4)
(3) = (4)
40 u + 100 = 35 u + 490
40 u - 35 u = 490 - 100
5 u = 390
1 u = 390 ÷ 5 = 78
Number of stickers that Adam has now
= 8 u + 20 + 5 u + 70
= 8 u + 5 u + 20 + 70
= 13 u + 90
= 13 x 78 + 90
= 1014 + 90
= 1104
Answer(s): 1104