In a jar, the ratio of the number of blue balls to the number of green balls was 1 : 3. Each time, 3 blue and 7 green balls were taken out of the jar. A while later, only 142 green balls were left in the jar. What was the total number of balls in the jar at first?
| |
Blue balls |
Green balls |
| Before |
1x3 =
3 u |
3x3 =
9 u |
| Change |
- 3 u |
- 7 u |
| After |
0 |
142 |
Since there is no blue balls left, this means that the number of blue marbles at first is the same as the number of blue marbles taken out.
Make the number of blue balls at first and taken out the same. LCM of 1 and 3 is 3.
Number of green balls in the end
= 9 u - 7 u
= 2 u
2 u = 142
1 u = 142 ÷ 2 = 71
Total number of balls in the jar at first
= 3 u + 9 u
= 12 u
= 12 x 71
= 852
Answer: 852
