In a jar, the ratio of the number of brown marbles to the number of silver marbles was 1 : 3. Each time, 4 brown and 7 silver marbles were taken out of the jar. A while later, only 90 silver marbles were left in the jar. What was the total number of marbles in the jar at first?
|
Brown marbles |
Silver marbles |
Before |
1x4 = 4 u |
3x4 = 12 u |
Change |
- 4 u |
- 7 u |
After |
0 |
90 |
Since there is no brown marbles 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 marbles at first and taken out the same. LCM of 1 and 4 is 4.
Number of silver marbles in the end
= 12 u - 7 u
= 5 u
5 u = 90
1 u = 90 ÷ 5 = 18
Total number of marbles in the jar at first
= 4 u + 12 u
= 16 u
= 16 x 18
= 288
Answer: 288