The answer is D. My dad taught me an easy way to solve those kind of problems.You need to do (60×20)÷100. And since 60 and 20 both have a zero and 100 has 2 zeros, u can cross out all the zeros and just do 6×2 and divide that by 1 and so 20% of 60 is 12. Hope this helped :)
3(5)-15+10(7)-2(5)
15-15+70-10
=60
The answer is 60
Let x be the number of mm of pure alcohol to be added:
I will add the mm to express the volume in mm
100mm.(19%) + (100%).x mL = (100 mL+x mL).(40%).
Now right again without the %
100.(0.19) + x.(1) = (100+x).(0.4)
19 + x = = 40 + 04x
x - 0.4x = 40 - 19
0.6 x = 21
x = 21/0.6 and x = 35 mL. This te quantity of pure alcohol should to be added to get a solution at 40%.
