Question

A rectangle is divided into four rectangles, and their respective areas are shown in the figure. (Figure is not drawn to scale). What is the missing area 'X' of the fourth rectangle?

$\begin{array}{cc}25& 20\\ 5& x\end{array}$

• A. 5sq units
• B. 2sq units
• C. 4sq units
• D. 2.5 sq units

Answer 1

The correct option is C

4sq units

Approach 1:

You can directly mark the answer as 25 $\times$ x = 20 $\times$ 5 $\Rightarrow$ x=4
Proof:
Observe that
ac = 25 sq units ....(1)
bc= 20 sq units ... (2)
ad = 5 sq units ... (3)
Dividing (1) by (3), we get: $\frac{c}{d}$ = 5 units ... (4)
Dividing (1) by (2) we get $\frac{a}{b}$ =5/4 units ... (5)
​St Multiplying (4) and (5) we get:
Sit $\frac{ac}{bd}$ = $\frac{25}{4}$ sq units
Since its already given that ac = 25 sq units, therefore the missing area 'X' =4 square units.

Approach 2:
Use the simple number approach to break up the values in each cell as shown below

thus x=4x1=4