SSC CGL 2025 Tier-I · 19 September 2025, Shift 3 · Quantitative Aptitude · Question 5 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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A & B together earn ₹840 for a job. A works the whole time; B joins after the job is 25 % done. B is twice as efficient as A. Find B’s share.

(a)₹ 420
(b)₹ 300
(c)₹ 360
(d)₹ 400

Answer

Why

Correct — A.
Rates: A = 1 unit per day, B = 2 units per day (twice as efficient)

First 25% of the job: A alone, so A does 25%
Last 75%: A and B together, split 1 : 2
A's part = 1⁄3 × 75% = 25%, B's part = 2⁄3 × 75% = 50%

Totals: A = 25% + 25% = 50%, B = 50%
Pay follows work: B = 50% of ₹840 = ₹420 → option (a)

Why the others are wrong

(b)
₹ 300 — ₹300 is 5⁄14 of ₹840, but B did exactly half the job, and pay is split in the ratio of work done.
(c)
₹ 360 — ₹360 is 3⁄7 of ₹840, a 4 : 3 split by time on the job (A all of it, B 75%) at equal rates. That reads '25 % done' as a quarter of the time and ignores B's double speed.
(d)
₹ 400 — ₹400 is 10⁄21 of ₹840, a little under half. B's work comes to exactly 50% of the job, so B's share is exactly ₹420.

Concept

Wages follow work done, and work done = rate × time. B's higher efficiency counts only for the part of the job B was present for.

Split the job at the moment B joins. A alone finishes the first 25%. For the remaining 75% both work, and at rates 1 : 2 that stretch divides into 25% for A and 50% for B.

A ends with 50% of the job and B with 50%, so the ₹840 splits equally.

Key facts

Pay for a shared job is divided in the ratio of work done
Work done = efficiency × time
When rates are 1 : 2, a joint stretch of work divides 1⁄3 : 2⁄3

Study next

Wages when one worker leaves before the job endsThree workers who join a job at different stagesTurning 'n times as efficient' into a ratio of days taken

Common traps

Splitting ₹840 in the efficiency ratio 1 : 2, which gives B ₹560 and ignores A's solo first quarter
Reading 'after the job is 25 % done' as 25% of the time rather than 25% of the work

The efficiency-to-rate step also decides 15 Sep 2025, 12:30, Quant Q.12, where A is 'three times more efficient' than B and the key, 22.5 days, reads that as a 3 : 1 rate.

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