In a pouch, the ratio of the number of pink balls to the number of red balls was 1 : 4. Each time, 4 pink and 7 red balls were taken out of the pouch. A while later, only 144 red balls were left in the pouch. What was the total number of balls in the pouch at first?
| |
Pink balls |
Red balls |
| Before |
1x4 =
4 u |
4x4 =
16 u |
| Change |
- 4 u |
- 7 u |
| After |
0 |
144 |
Since there is no pink balls left, this means that the number of pink marbles at first is the same as the number of pink marbles taken out.
Make the number of pink balls at first and taken out the same. LCM of 1 and 4 is 4.
Number of red balls in the end
= 16 u - 7 u
= 9 u
9 u = 144
1 u = 144 ÷ 9 = 16
Total number of balls in the pouch at first
= 4 u + 16 u
= 20 u
= 20 x 16
= 320
Answer: 320
