In a bottle, the ratio of the number of brown beads to the number of red beads was 1 : 4. Each time, 3 brown and 6 red beads were taken out of the bottle. A while later, only 90 red beads were left in the bottle. What was the total number of beads in the bottle at first?
| |
Brown beads |
Red beads |
| Before |
1x3 =
3 u |
4x3 =
12 u |
| Change |
- 3 u |
- 6 u |
| After |
0 |
90 |
Since there is no brown beads left, this means that the number of brown marbles at first is the same as the number of brown marbles taken out.
Make the number of brown beads at first and taken out the same. LCM of 1 and 3 is 3.
Number of red beads in the end
= 12 u - 6 u
= 6 u
6 u = 90
1 u = 90 ÷ 6 = 15
Total number of beads in the bottle at first
= 3 u + 12 u
= 15 u
= 15 x 15
= 225
Answer: 225
