It takes 4 tons of copper ore and 6 tons of iron ore to make one ton of alloy A. How many tons of alloy A can be made from 60 tons of copper ore and 90 tons of iron ore?  Choose the correct choice from the following answers:
A) 12 B) 15 C) 20 D) 30 E) 50
Yes, you need copper ore:iron ore in the ratio 4:6. Total 10 tons of the mix in this ratio will give 1 ton of alloy A.   If you have 60 tons of copper ore, it is enough for 60/4= 
<gadget id="calculator">60/4</gadget>
<output>15</output>
15 tons of alloy A.   If you have 90 tons of iron ore, it is enough for 90/6= 
<gadget id="calculator">90/6</gadget>
<output>15</output>
15 tons of alloy A.   Since iron ore is available for only 15 tons of alloy A, you can make only 15 tons of alloy A.   The leftover copper ore alone cannot make any alloy A and hence will be leftover only.   Answer must be 15.   (15)
<result>B</result>
It takes 4 tons of copper ore and 6 tons of iron ore to make one ton of alloy A. How many tons of alloy A can be made from 60 tons of copper ore and 90 tons of iron ore?