Q: How many stones of which color can be added to make the ratio 1:3?
Solution:
Existing sapphire: 25×2/5= 10.
1) If the ratio of blue to green is 1:3,
There are 10×3=30 emeralds.
Need to add greenstone: 30-25=5.
2) If the ratio of green to blue is 1:3,
There are 25×3=75 sapphires.
Need to add sapphire: 75- 10=65.