In a pouch, the ratio of the number of pink beads to the number of grey beads was 1 : 3. Each time, 3 pink and 7 grey beads were taken out of the pouch. A while later, only 180 grey beads were left in the pouch. What was the total number of beads in the pouch at first?
| |
Pink beads |
Grey beads |
| Before |
1x3 =
3 u |
3x3 =
9 u |
| Change |
- 3 u |
- 7 u |
| After |
0 |
180 |
Since there is no pink beads 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 beads at first and taken out the same. LCM of 1 and 3 is 3.
Number of grey beads in the end
= 9 u - 7 u
= 2 u
2 u = 180
1 u = 180 ÷ 2 = 90
Total number of beads in the pouch at first
= 3 u + 9 u
= 12 u
= 12 x 90
= 1080
Answer: 1080
