I kept 1/2 of my money in savings, and took half to the park, there I spent 1/5 on popcorn and 3/4 on rides. How much of my money did I not spend?
1/5 * 1/2 = 1/10.
3/4 * 1/2 = 3/8.
Bal.=1/2 - (1/10+3/8)=1/2-(4/40+15/40) =
1/2 - 19/40 = 20/40 - 19/40 = 1/40.