Question

John bought a mobile phone of length 4 inches and width 3 inches. What is the diagonal of the screen?

• A. 9 in
• B. 7 in
• C. 6 in
• D. 5 in

Answer 1

The correct option is D 5 in

Length of the mobile = 4 in
Width of the mobile = 3 in
The triangle formed in the mobile is shown below:

In $\Delta ABC,$
$\Rightarrow B{C}^2=A{B}^2+A{C}^2$ (by Pythagorean theorem)
$\Rightarrow B{C}^2=3^2+4^2$ (substitute 3 for AB and 4 for AC)
$\Rightarrow B{C}^2=9+16$ (evaluate the powers)
$\Rightarrow B{C}^2=25$
$\Rightarrow BC=\sqrt{25}$ (take the positive square for each side)
$\Rightarrow BC=5$
The diagonal of the screen = 5 in
Hence, the correct answer is option C.