Every tricycle sells for $4 and he has to make $50 , 
It means number of tricycles needed to make $50 = 

Number of tricycles cannot be in decimals , so round it off we get 13 
It means 13 tricycles are needed to be sold to make $50
Now 
Every tricycle has 2 pedals
So it means Number of pedals needed = 2*13 = 26 pedals