150*.8=120ltr ....30 ltr more solution can be added,. (120+30=150)Out of 120, 120*.9=108ltr alcho

150*.8=120ltr ....30 ltr more solution can be added,. (120+30=150)Out of 120, 120*.9=108ltr alcho, ,, and we have to make concentration less then 60% , which is less then 90 ltr of alchol out of 150ltr... So first we remove 3 times the solution by which alchol remain 81ltr out of 90ltr of solution ...Then add 6 time water to the solution ..Which make it 81 ltr out of 150 which is less then 60 ,,so ans should be B --6times

 

You can not remove 30 litres in one go...Because it is mentioned that you can remove solution only if there is no space to add.

 

Yes sir , but one by one ...First we need to fill 10ltr in 3 times.. which make 150 ltr of solution,which have 108 ltr of alchol.. den we start removing solution 10ltr in one go and add 10 ltr water till alchol remain less then 90ltr in solution of 150 ltr.