Solution:
Side of Square shaped region in which marigold plants are Planted = 140 miles
Area of The Square shaped region in which marigold plants are Planted
=Side × Side
=140 × 140
=19,600 square miles
Density of marigold plant =279 plants per square mile.
→→Total number of plants in the region = 19,600 × 279
=54,68,400
Now coming to Options,to find which expression product gives 5468400.
Option 1: ⇒ (3×102)×(2×104)=306 × 208=63648
Option 2: ⇒(3×102)×(2×105)=306 × 210=64260
Option 3: ⇒2×1043×102=212,772
Option 4: ⇒2×1042×102=212,568
→→None of the option gives , number of trees in the square region which is equal to 5468400.
None of the expression given , the researcher have most likely used when making her approximation for the number of marigold plants in the square shaped region.