
To find: Area of quadrilateral \( ABDE \)
Approach: The quadrilateral \( ABDE \) is made up of:
So, Area of \( ABDE = \) Area of rectangle \( ABCD \) + Area of triangle \( \triangle CDE \)
Step 1: Area of rectangle \( ABCD \)
Length = \( 7 - 3 = 4 \) units
Breadth = \( 5 \) units
Area = \( \text{Length} \times \text{Breadth} = 4 \times 5 = 20 \) square units
Step 2: Area of triangle \( \triangle CDE \)
Given: Base = \( 10 \) units, Height = \( 5 \) units
Area = \( \frac{1}{2} \times \text{Base} \times \text{Height} = \frac{1}{2} \times 10 \times 5 = 25 \) square units
Step 3: Total Area of Quadrilateral \( ABDE \)
\( = 20 + 25 = \mathbf{45} \) square units
Final Answer: (A) \( \mathbf{45} \)
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: