See the plants grow in airthemetic progression. day 1 its is 1 and day 2 it is 2, day 3 it is 4....... so, 1,2,4,6,8,...... so it take 48 days to fill the pond.. total plants = 48/2(2*1+(48-1)*2) total plants= 2304 so half the plants is 1152 so, 1152=n/2(2*1+(n-1)2) n=47 it so 47 days to complete half the pond.
