Colleen is selling tubs of popcorn to raise money for the school choir. Her goal is to raise $150. Colleen starts with 40 tubs of popcorn, and she has already sold 3/4 of them. If each tub of popcorn sells for $3.75, how much more money does Colleen need to raise to reach her goal?
Colleen has sold 40 x 3/4 = <<40*3/4=30>>30 tubs of popcorn.
So, she had 40 - 30 = <<40-30=10>>10 tubs of popcorn left.
Her earnings for the 30 tubs of popcorn is 30 x $3.75 = $<<30*3.75=112.5>>112.5
Therefore, Colleen still needs $150 - $112.5 = $<<150-112.5=37.5>>37.5. Answer: \boxed{37.5}.