Ratio

Question 1

In bag C, the ratio of red counters to yellow counters is 3:4. If 3 of the red counters are removed from bag C, the ratio of red counters to yellow counters is 3:5.

How many counters are in Bag C?

Answer 1

Bag C:
Before       After
R:Y.             R:Y
3:4              3:5
6:8.             6:10 
9:12.           9:15
12:16.         12:20
15:20

20 is the highest common multiple.

15-3 also equals 12