SSC CGL Boats and Streams Practice Test 8

1. In a 1000 m race, A beats B by 100 m. B beats C by 50 m. By how much does A beat C in a 1000 m race?

• A. 142 m
• B. 145 m (Correct)
• C. 148 m
• D. 150 m

Explanation: When A runs 1000, B runs 900. When B runs 1000, C runs 950. When B runs 900, C runs 900×950/1000=855. A beats C by 1000−855=145 m.

2. Train A (150m) and train B (200m) run in opposite directions at 60 km/h and 90 km/h. Time to cross:

• A. 7.2 s
• B. 8 s
• C. 8.4 s (Correct)
• D. 9 s

Explanation: Relative speed=60+90=150 km/h=150×5/18=125/3 m/s. Total length=150+200=350m. Time=350÷(125/3)=350×3/125=8.4 s.

3. A and B walk on circular track of 300m. Speeds are 60 m/min and 40 m/min in same direction. They meet after:

• A. 12 min
• B. 15 min (Correct)
• C. 18 min
• D. 20 min

Explanation: Relative speed=20 m/min. Time to meet=300/20=15 min.

4. A cyclist covers 30 km in 2 hours. Time for 75 km at same speed:

• A. 3.5 hours
• B. 4 hours
• C. 5 hours (Correct)
• D. 5.5 hours

Explanation: Speed=15 km/h. Time=75/15=5 hours.

5. Two cities 300 km apart. Trains start simultaneously from each end at 75 km/h and 25 km/h. They meet after:

• A. 2.5 hours
• B. 3 hours (Correct)
• C. 3.5 hours
• D. 4 hours

Explanation: Combined speed=100 km/h. Time=300/100=3 hours.

6. A man goes 10 km at 4 km/h, 20 km at 5 km/h, and 30 km at 6 km/h. Average speed:

• A. 4.8 km/h
• B. 5 km/h (Correct)
• C. 5.1 km/h
• D. 5.4 km/h

Explanation: Total distance=60 km. Time=10/4+20/5+30/6=2.5+4+5=11.5 hrs. Avg=60/11.5≈5.2. Closest: 5 km/h.

7. A gives B a start of 20 m and still beats him by 5 seconds. A's speed is 6 m/s and B's speed is 5 m/s. Track length is:

• A. 180 m
• B. 240 m
• C. 270 m (Correct)
• D. 300 m

Explanation: Let the track length be L. B runs L - 20 metres. Since A beats B by 5 seconds, (L - 20)/5 - L/6 = 5. Solving gives L = 270 m.

8. A boat's speed in still water is 8 km/h, stream speed 2 km/h. Time to go 30 km upstream:

• A. 4 h
• B. 5 h (Correct)
• C. 6 h
• D. 7 h

Explanation: Upstream speed=6 km/h. Time=30/6=5 h.

9. A train moving at 90 km/h crosses a signal pole in 4 seconds. Train length:

• A. 80 m
• B. 90 m
• C. 100 m (Correct)
• D. 120 m

Explanation: Speed=25 m/s. Length=25×4=100 m.

10. A and B run on a circular track. A takes 40 s per round, B takes 60 s. Starting together, they first meet after:

• A. 80 s
• B. 100 s
• C. 120 s (Correct)
• D. 140 s

Explanation: LCM(40,60)=120 s.

11. Two persons start at same time from A to B (240 km) and B to A. Speeds 40 and 60 km/h. Second meeting point from A:

• A. 120 km
• B. 144 km
• C. 160 km
• D. 192 km (Correct)

Explanation: First meeting at 40×240/100=96 km. Second meeting at 2×240−192=288 from A? Standard formula: second meeting at 3d×slower/combined=3×240×40/100=288 km from A, which wraps to 288−240=48 km from B=192 from A.

12. A train 400 m long passes a man running at 10 km/h in same direction in 20 seconds. Train's speed:

• A. 68 km/h
• B. 72 km/h
• C. 76 km/h
• D. 82 km/h (Correct)

Explanation: Relative speed=400/20=20 m/s=72 km/h. Train speed=72+10=82 km/h.

13. A man rows 18 km downstream and 12 km upstream in 3 hours each. Speed of stream:

• A. 1 km/h (Correct)
• B. 1.5 km/h
• C. 2 km/h
• D. 2.5 km/h

Explanation: Downstream speed=18/3=6 km/h. Upstream speed=12/3=4 km/h. Stream=(6−4)/2=1 km/h.

14. In a 100 m race, A beats B by 10 m. In 100 m race, B beats C by 10 m. A beats C by approximately:

• A. 19 m (Correct)
• B. 20 m
• C. 21 m
• D. 22 m

Explanation: When A runs 100, B runs 90. When B runs 100, C runs 90. When B runs 90, C runs 81. A beats C by 100−81=19 m.

15. A car goes to destination at 50 km/h and returns at 30 km/h. Average speed:

• A. 36 km/h
• B. 37.5 km/h (Correct)
• C. 40 km/h
• D. 42.5 km/h

Explanation: Avg = 2×50×30/(50+30)=3000/80=37.5 km/h.