There are some red counters and some yellow counters in a bag in the ratio 1 : 5There are 20 yellow counters in the bag. Janet puts some more red counters into the bag. The ratio of the number of red counters to the number of yellow counters is now 1 : 2 How many red counters does Janet put into the bag?
5 out of (1+5= 6) are yellow
5/6 = 20 so there are 24 total ....meaning 4 are red
if you add x red marbles to the 4 they become 1/3 of the total
(4+x)/ (24+x) =1/3 cross multiply
12 + 3x = 24+x
2x = 12
x = 6 ===== reds added now there are 10 out of 30 reds 20 out of 30 are yellow ratio 1:2