The Lcm is 104. The lcm of 13 and 8 is the smallest positive integer that divides the numbers 13 and 8 without a remainder. Spelled out, it is the least common multiple of 13 and 8. Here you can find the lcm of 13 and 8, along with a total of three methods for computing it. In addition, we have a calculator you should check out. Not only can it determine the lcm of 13 and 8, but also that of three or more integers including thirteen and eight for example. Keep reading to learn everything about the lcm (13,8) and the terms related to it.
Answer:
58.33 lbs.
Step-by-step explanation:
There are already 25 lbs of alloy of copper
Of this 25 lbs, 20% is pure i.e. copper content = 25(0.5) = 5lbs.
Now available is
Copper Other metals
5 lbs 20 lbs
Let x lb of 30% copper is added.
Then new alloy will have 5+0.3x lb copper in total of 25+x lbs
Percentage pure = 
Simplify to get
Hence answer is 58.33 lbs should be added.
I could be wrong but i believe it's six
