In the first week, the tree shed 2/5*1000 = <<2/5*1000=400>>400 leaves.
The number of leaves remaining on the tree at the end of the first week is 1000-400 = <<1000-400=600>>600
In the second week, the tree shed 40/100*600 = <<40/100*600=240>>240 leaves.
The number of leaves remaining on the tree is 600-240 = <<600-240=360>>360
The third week the tree shed 3/4 of its leaves, a total of 3/4*360 = <<3/4*360=270>>270 leaves.
The number of leaves remaining on the tree is 360-270 = <<360-270=90>>90 leaves.
#### 90