Answer: 210 yards of fencing will be needed
Step-by-step explanation: well the perimeter of this rectangular field is 21 + 63 + 21 + 63 yards or 2(21) + 2(63) yards which equals 168 yards.
To divide the field into 3 equal parts, u need to divide the length (63 yards) into 3 parts which also requires two more lines of fencing.
63/3=21 which means u get squares perfect squares when u divide. now that means that's an additional 21*2 yards of fencing since you need two more rows of fencing in the middle of the field to divide the length into three equal parts. 21*2 = 42 so thats an additional 42 yards. The total amount of fencing is 168 + 42 = 210 yards.