SSC CGL 2025 Tier-I · 15 September 2025, Shift 3 · Quantitative Aptitude · Question 20 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

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The cost of fencing a circular ground at ₹120/m is ₹3,768. Find the radius of the ground.

(a)5 m
(b)10 m
(c)15 m
(d)20 m

Answer

Why

Correct — A. Fencing is paid per metre of boundary, so the cost gives the circumference.

Circumference: 3,768 ÷ 120 = 31.4 m

2πr = 31.4
With π = 3.14: 6.28r = 31.4
Divide by 6.28: r = 5 m → option (a)

Why the others are wrong

(b)
10 m — 10 m is the diameter. Dividing 31.4 by π gives d = 10 m. The question asks for the radius, which is half of that.
(c)
15 m — 15 m gives a boundary of 2 × 3.14 × 15 = 94.2 m, and fencing it at ₹120/m costs ₹11,304, three times ₹3,768.
(d)
20 m — 20 m gives 2 × 3.14 × 20 = 125.6 m of boundary, costing ₹15,072 at ₹120/m, four times the ₹3,768 stated.

Concept

Fencing is priced per metre of boundary, so total cost ÷ rate = perimeter. For a circle the perimeter is the circumference, 2πr.

Levelling, turfing or painting is priced per square metre instead, and the same division then gives the area, πr².

The stem gives no value of π. 31.4 = 10 × 3.14 points to π = 3.14. With 22⁄7 the radius is 31.4 × 7 ⁄ 44 ≈ 4.995 m, still 5 m to the nearest option.

Key facts

Fencing cost ÷ rate per metre = length of the boundary.
Circumference = 2πr = πd.
With π = 3.14, a circumference of 31.4 m means a diameter of 10 m.

Study next

Cost of turfing or levelling a circular plot at a rate per square metreFencing a rectangular field from its area and the ratio of its sidesRadius of a wheel from the revolutions it makes over a distance

Common traps

Dividing 31.4 by π and stopping at 10 m, which is the diameter.
Treating the cost as buying area: πr² = 31.4 gives r ≈ 3.16 m, which matches no option.

Circumference as a length also decides 25 Sep 2024, 12:30, Quant Q.15: a circle whose circumference equals those of radii 12 cm and 16 cm together has radius 28 cm, so diameter 56 cm.

Pricing per square metre turns cost into area: 14 Sep 2025, 09:00, Quant Q.22 paints 90% of a circular board of radius 2 m at ₹60 per m², keyed ₹678.6.

Related PYQs

No directly related past PYQ was found.

Topic: Triangle, Quadrilaterals, Regular Polygons, Circle — all 65 SSC CGL questions on it, every solved shift.