Alice should mow 20*40/2 or 400 m^2 (mowing half of the lawn) or 400 m^2 (not mowing half of the lawn)
after the first round 18*38 m^2 of lawn is not mowed
after the second round 16*36 m^2 isn't mowed
after the third round 14*34 m^2 isn't mowed
76 m^2 is left not mowed (14*34=476), hence we need to mow 76 m^2 lawn still
the dimensions of round will be 12 by 32

Alice will be mowing (476-384) in one, the fourth round which is 1 round (92 m^2)

92 m^2 --> 100%
76 m^2 --> x%, x=0.8

[spoiler]c 3.8 round
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quantskillsgmat wrote:Alice has to mow a rectangular lawn with dimension 20m by 40m.he has a lawn mover, which can mow a strip of 1 m at a time .he starts from a corner and moves parellol to the sides and towards center.how many rounds wd he have made of the lawn,when half of the lawn is mowed.
a)2.5 b)3.5 c)3.8 d)4