In a jar, the ratio of the number of silver balls to the number of grey balls was 1 : 4. Each time, 4 silver and 6 grey balls were taken out of the jar. A while later, only 140 grey balls were left in the jar. What was the total number of balls in the jar at first?
| |
Silver balls |
Grey balls |
| Before |
1x4 =
4 u |
4x4 =
16 u |
| Change |
- 4 u |
- 6 u |
| After |
0 |
140 |
Since there is no silver balls left, this means that the number of silver marbles at first is the same as the number of silver marbles taken out.
Make the number of silver balls at first and taken out the same. LCM of 1 and 4 is 4.
Number of grey balls in the end
= 16 u - 6 u
= 10 u
10 u = 140
1 u = 140 ÷ 10 = 14
Total number of balls in the jar at first
= 4 u + 16 u
= 20 u
= 20 x 14
= 280
Answer: 280
