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Question

A triangular board has sides 9 cm, 10 cm, and 17 cm. A circle passes through all three vertices. Find the circumradius.

This question was previously asked in
UPTET 2026 Paper 2 Social Studies Question Paper (3-Jul-2026) (Shift 1)
The correct answer is

10.625 cm

Using Heron's formula, the semi-perimeter is \(s = \frac{9 + 10 + 17}{2} = 18\).

The area is \(\text{Area} = \sqrt{18 \times 9 \times 8 \times 1} = \sqrt{1296} = 36\) square cm.

The circumradius formula is \(R = \frac{a \times b \times c}{4 \times \text{Area}}\).

Substituting the values gives \(R = \frac{9 \times 10 \times 17}{4 \times 36} = \frac{1530}{144} = 10.625\) cm.

Hence, the circumradius of the triangle is 10.625 cm.

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Important Questions from Geometry

  1. ABCDEF is a regular hexagon. Side of the hexagon is 36 cm. What is the area of the triangle AOB ?

  2. If ∆ABC ~ ∆DEF, and BC = 4 cm, EF = 5 cm and the area of triangle ABC = 80 cm 2, then the area of the triangle DEF is:

  3. If Δ ABC is right angled at B, AB = 12 cm and ∠CAB = 60°, determine the length of BC.  

  4. If ΔABC and ΔDEF are congruent triangles, then which of the following is FALSE?

  5. D and E are points on the sides AB and AC, respectively, of ΔABC such that DE is parallel to BC and AD ∶ DB = 7 ∶ 9. If CD and BE intersect each other at F. then find the ratio of areas of ΔDEF and ΔCBF.

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