There are some red and pink balls in a box. If 9 red balls are removed from the box, the total number of balls left will be 6 times the number of red balls left. If 9 pink balls are removed from the box, the total number of balls left will be 3 times the number of red balls. How many balls are there in the box?
|
Case 1 |
Case 2 |
|
Red balls |
Pink balls |
Red balls |
Pink balls |
Before |
1 u + 9 |
5 u |
1 p |
2 p + 9 |
Change |
- 9 |
|
|
- 9 |
After |
1 u |
5 u |
1 p |
2 p |
Number of pink balls in the end for Case 1
= 6 u - 1 u
= 5 u
Number of red balls in the end for Case 2
= 3 p - 1 p
= 2 p
The number of red balls at first is the same for Case 1 and Case 2.
The number of pink balls at first is also the same for Case 1 and Case 2.
1 u + 9 = 1 p --- (1)
5 u = 2 p + 9
5 u - 9 =
2 p --- (2)
Make p the same.
(1)
x2 2 u + 18 =
2 p --- (3)
(2) = (3)
5 u - 9 = 2 u + 18
5 u - 2 u = 18 + 9
3 u = 27
1 u = 27 ÷ 3 = 9
Number of balls in the box
= (1 u + 9) + 5 u
= 6 u + 9
= (6 x 9) + 9
= 54 + 9
= 63
Answer(s): 63