20x40 = 800 m2
19x40 = 760 m2
19x39 = 741 m2
18x39 = 702 m2
18x38 = 684 m2 (one time)
17x38 = 646 m2
17x37 = 629 m2
16x37 = 592
16x36 = 576 m2 (two times)
15x36 = 540 m2
15x35 = 525 m2
14x35 = 490 m2
14x34 = 476 m2 (three times)
13x34 = 442 m2
13x33 = 429 m2
12x33 = 396 m2 (< 400 m2, therefore appr. 3.7 times)
12x32 = 384 m2

Todd will have to go around approximately 3.7 times until he finishes mowing his half.

Rui