Question 264388
let there is 100 ml of original solution

in that there is 60% that is 60 ml of orange content

now suppose x ml of water is added 

so total it is 100+x ml and orange content is 60 ml

now this 60 ml should constitute 40% of 100+x

60=(40/100)(100+x)

60=40+.4x

.4x=20

x=50 ml

so 50% of water should be added