Question

In the given figure, AD = BC. What is the length of AB if DC = 4 cm?

• A. 5 cm
• B. 4 cm
• C. 3 cm
• D. Can’t find

Answer 1

The correct option is B

4 cm

In $\Delta$ABC and $\Delta$ADC, we have

AD = BC (given)
AC = AC (common side)
and $\angle$ADC = $\angle$ABC = 90${}^{\circ }$
Thus, $\Delta$ABC $\cong$ $\Delta$ADC ... (RHS Postulate)

Therefore, AB = DC = 4 cm (corresponding parts of congruent triangles)