All Exams Test series for 1 year @ ₹349 only
Question

ABC is a triangle right-angled at B. If \(\text{AC} = \frac{(p+q)}{2}\) and \(\text{BC} = \frac{(p-q)}{2}\), then which of the following statements is/are correct ?
I. The value of AB is equal to the geometric mean of p and q.
II. The perimeter of the triangle is \(p(q+1)\).
Select the answer using the code given below :

This question was previously asked in
CDS 1 2026 Maths Question Paper (12-Apr-2026)
The correct answer is
I only

Right-Angled Triangle Properties

We are given a triangle ABC, which is right-angled at vertex B.

  • The length of the hypotenuse AC is given as \(\frac{(p+q)}{2}\).
  • The length of one side BC is given as \(\frac{(p-q)}{2}\).

Calculating Side AB using Pythagorean Theorem

According to the Pythagorean theorem in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. So, \(AB^2 + BC^2 = AC^2\).

We can rearrange this to find the length of side AB:

\(AB^2 = AC^2 - BC^2\)

Substitute the given values for AC and BC:

\(AB^2 = \left(\frac{p+q}{2}\right)^2 - \left(\frac{p-q}{2}\right)^2\)

Expand the squares and combine the terms:

\(AB^2 = \frac{(p+q)^2}{4} - \frac{(p-q)^2}{4}\)

\(AB^2 = \frac{1}{4} \left[ (p+q)^2 - (p-q)^2 \right]\)

Using the algebraic identity \((a+b)^2 - (a-b)^2 = 4ab\), where \(a=p\) and \(b=q\):

\(AB^2 = \frac{1}{4} [4pq]\)

\(AB^2 = pq\)

Taking the square root to find the length of AB:

\(AB = \sqrt{pq}\)

Evaluating Statement I: Geometric Mean

Statement I asserts that the value of AB is equal to the geometric mean of p and q.

The geometric mean (GM) of two numbers \(p\) and \(q\) is calculated as \(\sqrt{pq}\).

Our calculation shows that \(AB = \sqrt{pq}\).

Therefore, Statement I is correct.

Evaluating Statement II: Triangle Perimeter

Statement II claims that the perimeter of the triangle is \(p(q+1)\).

The perimeter of triangle ABC is the sum of its sides: AB + BC + AC.

Perimeter = \(\sqrt{pq} + \frac{(p-q)}{2} + \frac{(p+q)}{2}\)

Combine the terms for BC and AC:

Perimeter = \(\sqrt{pq} + \frac{(p-q) + (p+q)}{2}\)

Perimeter = \(\sqrt{pq} + \frac{2p}{2}\)

Perimeter = \(\sqrt{pq} + p\)

Statement II proposes the perimeter is \(p(q+1)\), which expands to \(pq + p\).

Comparing the calculated perimeter (\(\sqrt{pq} + p\)) with the proposed perimeter (\(pq + p\)), we see they are not equal in general.

Therefore, Statement II is incorrect.

Final Conclusion

Based on the analysis, only Statement I is correct.

Was this answer helpful?

Important Questions from Geometry

  1. The sides of a triangle are in the ratio 6 : 4 : 3 and its perimeter is 104 cm. The length of the longest side (in cm) is:

  2. An isosceles right-angled triangle has hypotenuse length as 10 units. What is the area of the triangle (in square units)?

  3. Two circles of radii 16 cm and 4 cm, respectively, touch each other externally at Point A. PQ is the direct common tangent of these circles with centres C1 and C2, respectively. What is the length of PQ?

  4. Let C be a circle with center O and AB be a chord of C such that the length of AB is equal to the radius of C. Let D be any point on the major arc of AB. Find ∠AOB and ∠ADB, respectively.

  5. The centres of two circles are 84 cm apart. If the radii of these two circles are 38 cm and 26 cm, respectively, then which of the following options gives the length (in cm) of a direct common tangent of these two circles?

Need Expert Advice?
Upcoming Exams
NDA
September 13, 2026
CDS
September 13, 2026
Test Series
CDS img
Defence
UPSC CDS 2026 Mock Test Series
540 Tests 4 Tests Free
1135 Attempts
4.3(168)
English, Hindi
More Questions from CDS

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App