The distance between the parallel sides of a trapezium of area 27.5 cm² is 5 cm. If the length of one of those two parallel sides is 7.5 cm, then the length of the other side is :

1. 3.5 cm

2. 7 cm

3. 8.5 cm

4. 9 cm

Let the length of other parallel side be a cm.

By formula,

Area of trapezium = $\dfrac{1}{2}$ × (sum of parallel sides) × distance between parallel sides

⇒ 27.5 = $\dfrac{1}{2}$ × (7.5 + a) × 5

⇒ 55 = (7.5 + a) × 5

⇒ 7.5 + a = $\dfrac{55}{5}$

⇒ 7.5 + a = 11

⇒ a = 11 - 7.5 = 3.5 cm.

Hence, option 1 is the correct option.