1.A can do a piece of work in 60 days while B can do it in 75 days. They begin together but 20 days before the completion of the work, A leaves off. How many days B finishes the remaining work?
1).A’s one day work = 1/60
B’s one day work = 1/75
(A+B)’s one day work = (1/60+1/75) = 3/100
Both A and B complete the work in 20 days = 20 × (3/100) = 3/5
∴ remaining (1-3/5 = 2/5) 2/5th work is done by B = 2/5 × 75 = 30 days.
Answer: D
2.A and B can do a job in 15 days, B and C can do a job in 20 days and C and A can do it in 12 days. How long would C take to do that job?B’s one day work = 1/75
(A+B)’s one day work = (1/60+1/75) = 3/100
Both A and B complete the work in 20 days = 20 × (3/100) = 3/5
∴ remaining (1-3/5 = 2/5) 2/5th work is done by B = 2/5 × 75 = 30 days.
Answer: D
2).(A+B)’s one day work = 1/15
(B+C)’s one day work = 1/20
(C+A)’s one day work = 1/12
The work done by (A+B+C) is= 2(A+B+C) = 1/15+1/20+1/12 = 1/5
∴ (A+B+C)’s one day work = ½ × 1/5 = 1/10
Hence, C can do a job in one day = 1/10 – 1/15 = 5/150 = 1/30
∴ C can finish the job in 30 days.
Answer: B
(B+C)’s one day work = 1/20
(C+A)’s one day work = 1/12
The work done by (A+B+C) is= 2(A+B+C) = 1/15+1/20+1/12 = 1/5
∴ (A+B+C)’s one day work = ½ × 1/5 = 1/10
Hence, C can do a job in one day = 1/10 – 1/15 = 5/150 = 1/30
∴ C can finish the job in 30 days.
Answer: B
3.A contractor undertook to finish a certain work in 144 days and employed 120 men. After 64 days, he found that he had already done 2/3 of the work. How many men can be discharged now, so that the work may finish in time?
3).Work = Men × Day
W1/W2 = (M1 × D1) / (M2 × D2)
[(2/3) W] / [(1/3) W] = (120×64) / (M2 × 80)
2×M2 × 80 = 120× 64
M2 = 48
Hence, 120 – 48 = 72 men can be discharged.
Answer: C
W1/W2 = (M1 × D1) / (M2 × D2)
[(2/3) W] / [(1/3) W] = (120×64) / (M2 × 80)
2×M2 × 80 = 120× 64
M2 = 48
Hence, 120 – 48 = 72 men can be discharged.
Answer: C
4.A, B and C can do a piece of work in 36, 48 and 72 days respectively. They started the work but A left 9 day before the completion of the work while B left 12 days before the completion of the work. How many days C worked?
4).Let C can complete the work in X days
(X-9)/36 + (X-12)/48 + (X/72) = 1 work
(12(X-9) + 9(X-12) + 6X)/432 = 1
12X -108 +9X -108 +6X = 432
∴ X= 648/27 = 24
Hence, C worked for 24 days.
Answer: B
5.A ,B and C can do a piece of work in 40 days, 30 days and 60 days respectively. A works continuously, on every third day A is assisted by B and C. In how many days work is completed?(X-9)/36 + (X-12)/48 + (X/72) = 1 work
(12(X-9) + 9(X-12) + 6X)/432 = 1
12X -108 +9X -108 +6X = 432
∴ X= 648/27 = 24
Hence, C worked for 24 days.
Answer: B
5). Day1 Day2 Day3 … A A A+B+C The above cycle is repeated for the next days.
The work done by A, B and C in one day is 1/30, 1/40 and 1/60
Hence, 3 (3A+B+C) = 3 [1/40] + [1/30] + [1/60]
= 3(3) +4 +2 /120 = 15/120 = 1/8
∴ (3A+B+C) = 1/8×3 = 1/24
Hence, the work can be completed in 24 days.
Answer: D
The work done by A, B and C in one day is 1/30, 1/40 and 1/60
Hence, 3 (3A+B+C) = 3 [1/40] + [1/30] + [1/60]
= 3(3) +4 +2 /120 = 15/120 = 1/8
∴ (3A+B+C) = 1/8×3 = 1/24
Hence, the work can be completed in 24 days.
Answer: D
6.A work is started by 15 men. After 4 days, 3 more men accompanied them to finish the work in next 10 days. How many men should have started the work to finish it in 8 days?
6). Work = Men × Days
(15×4) + (15+3) ×10 = M × 8
60 + 180 = M × 8
∴ M = 240/8 = 30
Hence, 30 men are required to finish the work in 8 days.
Answer: C
(15×4) + (15+3) ×10 = M × 8
60 + 180 = M × 8
∴ M = 240/8 = 30
Hence, 30 men are required to finish the work in 8 days.
Answer: C
7.A can finish a work in 8 days. After working for 3 days, B is joined and the remaining work got finished in next one day. If B works alone, how many days will be required to finish the work?
7).Total work = A × 8 = A ×3 + (A+B) ×1
8A = 3A + A + B
∴ B = 4A
Number of days to finish the work by B = ¼ (No. of days of A)
= ¼ × 8 = 2 days.
Answer: A
8.Two taps A and B fill an overhead tank in 10 hrs and 15 hrs respectively. Both the taps are opened for 4 hrs and then B is turned off. How much time will A take to fill the remaining tank?8A = 3A + A + B
∴ B = 4A
Number of days to finish the work by B = ¼ (No. of days of A)
= ¼ × 8 = 2 days.
Answer: A
8).Tank filled in 1 hr by tap A = 1/10
Tank filled in 1 hr by tap B = 1/15
Both taps filled in 4 hrs = 4(1/10 + 1/15)
= 4 (1/6) = 2/3
∴ remaining 1-2/3 = 1/3 of the tank is filled by tap A = 1/3 ×10
= 3/10 = 3 1/3 hrs.
Answer: B
9.A boiler can be filled by two taps in 20 min and 30 min respectively and can be emptied by a third tap in 48 min. If they are all turned on at once, when will the boiler be half full?Tank filled in 1 hr by tap B = 1/15
Both taps filled in 4 hrs = 4(1/10 + 1/15)
= 4 (1/6) = 2/3
∴ remaining 1-2/3 = 1/3 of the tank is filled by tap A = 1/3 ×10
= 3/10 = 3 1/3 hrs.
Answer: B
9).A boiler is filled by 2 taps= 1/20 + 1/30 = 5/60 = 1/12
∴ half full the boiler = ½ B = 1/12 – 1/48
= 3/ 48 = 1/16
B = 2/16 =1/8
Hence, 8 mins required to half fill the boiler.
Answer: D
∴ half full the boiler = ½ B = 1/12 – 1/48
= 3/ 48 = 1/16
B = 2/16 =1/8
Hence, 8 mins required to half fill the boiler.
Answer: D
10.If 8 women or 12 children can do a piece of work in 16 days, what is the number of days required to complete the work by 20 women and 6 children?
10).8 women = 12 children
1 W = 12/8 C = 3/2 C
∴ 20 W = 20 × 3/2 C = 30 C
(12 C) ×16 = (20 W + 6 C) × D
(12 C) ×16 = (30 C + 6 C) × D
D = 12 C × 16 / 36 C
= 16 /3 = 5 1/3 days.
Answer: C
1 W = 12/8 C = 3/2 C
∴ 20 W = 20 × 3/2 C = 30 C
(12 C) ×16 = (20 W + 6 C) × D
(12 C) ×16 = (30 C + 6 C) × D
D = 12 C × 16 / 36 C
= 16 /3 = 5 1/3 days.
Answer: C
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