SSC CGL 2024 Tier-I · 24 September 2024, Shift 3 · Quantitative Aptitude · Question 21 of 99

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

The given pie-chart shows the data on A, B, O, and AB blood groups of 240 donors. Study the chart and answer the question that follows. What is the ratio of the average donors of blood groups ‘A’, ‘O’, and ‘AB’ to the donors of blood group ‘B’?

(a)4 : 3
(b)3 : 4
(c)1 : 3
(d)2 : 3

Answer

Why

Correct — D. Donors are proportional to sector angle, so the ratio can be settled in degrees alone and the figure of 240 never has to be used.

From the pie: A = 90°, B = 120°, O = 80°, AB = 70° (sum 360°)
A + O + AB = 90 + 80 + 70 = 240°
Average of those three = 240 ⁄ 3 = 80°

Ratio = 80° : 120° = 2 : 3 → option (d).

Why the others are wrong

(a)
4 : 3 — 4 : 3 is 120 : 90, that is B measured against A alone. It leaves out the O and AB sectors that the word "average" requires you to include.
(b)
3 : 4 — 3 : 4 is 90 : 120, A alone against B. The three groups average 80°, not A's 90°, so the first term is wrong.
(c)
1 : 3 — 1 : 3 needs an average sector of 40°, one third of B's 120°. The three sectors average twice that, so the mean is two-thirds of B, not one-third.

Concept

A pie chart's whole is 360°, and every quantity in it is a fixed multiple of its sector angle. Here that multiplier is 240 ⁄ 360 = 2/3 of a donor per degree.

In a ratio, that multiplier appears in both terms and cancels. So a question asking only for a ratio of donor counts can be answered on the angles, which are whole numbers, instead of on the counts, which need not be.

The other word to read carefully is average: it asks for the mean of the three sectors, so add the three angles and divide by 3 before comparing with B.

The 240 donors do not divide cleanly across the sectors: O's 80° works out to 53.33 donors and AB's 70° to 46.67, while only A (60) and B (80) come out whole. Working in degrees sidesteps that; converting first and rounding will bend the ratio.

Key facts

The four sectors in this chart are A 90°, B 120°, O 80° and AB 70°, adding to 360°.
Donors per degree here is 240 ÷ 360 = 2/3, a constant that cancels out of any ratio.
The mean of the A, O and AB sectors is 80°, against B's 120°.
A ratio of two quantities from one pie chart equals the ratio of their central angles.

Study next

Converting a percentage share into a central angle and backCombining two sectors and expressing them as a percentage of the wholeComparing one sector against the sum of the remaining sectors

Common traps

Comparing the summed 240° with B's 120° and reporting 2 : 1, forgetting to average.
Converting to donors first and rounding 53.33 and 46.67 before forming the ratio.
Writing the ratio the wrong way round as 3 : 2.

SSC labels pie sectors either in degrees, as here, or in percentages — 13 Sep 2024, 12:30, Quant Q.23 gives percentage shares of a batsman's 440 runs, and 23 Sep 2024, 12:30, Quant Q.3 runs the conversion the other way, asking for the central angle of one head of publishing expenditure.

Related PYQs

No directly related past PYQ was found.