Explanation:
so, the scale is 1/4 cm to 1 m.
1 m = 100 cm.
1 m² = 100×100 = 10,000 cm²
that means the scaling factor is 0.25/100 = 1/400
(after multiplying with 4/4).
so, every length in reality has to be multiplied by 1/400 to get the length on the plan.
the area of a rectangle is
length × width.
now, applying the scaling factor means that
length×1/400 × width×1/400 = 40
length × width × 1/400×1/400 = actual area × 1/400² = 40
actual area = 40×400² = 6,400,000 cm²
= 6,400,000 / 10,000 = 640 m²