Solution
GivenIn this question, we are given that
To findWe need to determine
• The area of the triangle ALC
Approach and WorkingAs ABCD is a rectangle, each of the angles of the rectangle is 90
• Thus, we can infer that both ADL and ACB are right-angle triangles (as angle ADL = angle ABC = 90)
Considering triangle ADL, AD = 3 and AL = 5.
• Hence, following the Pythagorean triplet of 3-4-5, we can infer that DL = 4
• So, area of triangle ADL = ½ x AD x DL = ½ x 3 x 4 = 6
Similarly, considering triangle ACB, AB = 7 and BC = AD = 3
• So, area of triangle ACB = ½ x AB x BC = ½ x 7 x 3 = 10.5
From the given diagram, we can also
visualise that
• Area of triangle ADL + area of triangle ALC + area of triangle ACB = area of rectangle ABCD = 3 x 7 = 21
Or, 6 + ALC + 10.5 = 21
Or, ALC = 21 – 6 – 10.5
Or, ALC = 4.5
Thus, option E is the correct answer.
Correct Answer: Option EFor more details on the terms "Infer" and "Visualize", click on the image below
