There was an equal number of yellow and grey balls in a box at first. After 10 grey balls were taken out and 50 yellow balls were added into the box, there was
17 as many grey balls as yellow balls. Find the number of grey balls in the box at first.
| |
Yellow balls |
Grey balls |
| Before |
7 u - 50 |
1 u + 10 |
| Change |
+ 50 |
- 10 |
| After |
7 u |
1 u |
The number of yellow and grey balls in the box is the same at first.
7 u - 50 = 1 u + 10
7 u - 1 u = 10 + 50
6 u = 60
1 u = 60 ÷ 6 = 10
Number of grey balls at first
= 1 u + 10
= 10 + 10
= 20
Answer(s)20
