Sam needs to make a drink from orange cordial and lemonade in the ratio 1:9. How much orange cordial does he need to make 1500ml?

1 portion of orange cordial is mixed with 9 portions of lemonade

There are 10 portions in total 

one-tenth of the total volume would be the volume of orange cordial needed 

(1/10) * 1500 = 150 

Therefore 150ml of orange cordial is needed