Directions(1-5): What should come in place of (_) in the following series:
1. 9, 17, 37, 71, 121, _
A. 179
B. 189
C. 199
D. 209
E. None of these
Sol. B) 189
Difference of the difference is in A.P. of 12, 14, 16, 18.
2. 5, 8, 27, 104, 525, _
A. 3125
B. 3150
C. 3144
D. 3156
E. None of these
Sol. 5*2 - 2 = 8
8*3 + 3 = 27
27*4 - 4 = 104
104*5 + 5 = 525
525*6 - 6 = 3144.
3. 1, 3, 7, 13, 21, _
A. 30
B. 31
C. 32
D. 33
E. None of these
Sol. 1 + 2*1 = 3
3 + 2*2 = 7
7 + 2*3 = 13
13 + 2*4 = 21
21 + 2*5 = 31.
4. 30, 16, 10, 8, 8, _
A. 12
B. 9
C. 6
D. 15
E. None of these
Sol. 30/2 + 1 = 16
16/2 + 2 = 10
10/2 + 3 = 8
8/2 + 4 = 8
8/2 + 5 = 9.
5. 7, 11, 19, 29, 41, _
A. 56
B. 55
C. 54
D. 53
E. None of these
Sol. 4 + 1 = 5
9 + 2 = 11
16 + 3 = 19
25 + 4 = 29
36 + 5 = 41
49 + 6 = 55.
6. A boat whose speed 15 km/h in still water goes 30 km downstream and comes back in four and half hours. The speed of the stream is (in km/hr)
A. 5
B. 3
C. 8
D. 9
E. None of these
Sol. Lets assue speed of the stream is 'x' km/hr.
Then,
30/(15-x) + 30/(15+x) = 9/2
Solving, x = 5 km/hr.
7. A car covers a distance of 210 km in a certain amount of time at the speed of 35 km/h. What is the average speed of a truck that travel distance of 18 km less than the car in the same time?
A. 34 km/hr
B. 36 km/hr
C. 35 km/hr
D. 32 km/hr
E. None of these
Sol. Time = 210/35 = 6hrs.
Speed of truck = (210-18)/6 = 32 km/hr.
8. If a person walks at 14 km/h instead of 10 km/h he would have walked 20 km more. The actual distance travelled by him is-
A. 85 km
B. 50 km
C. 80 km
D. 70 km
E. None of these
Sol. x/10 = (x+20)/14
Soling, x = 50 km.
9. A train running at a speed of 40 m/s crosses a pole in 21 seconds less than the time it required to cross a bridge 3.5 times its length at the same speed. What is the length of bridge?
A. 1080 m
B. 240 m
C. 840 m
D. 560 m
E. None of these
Sol. Let the lengtth of the train be 'x' meter.
Length of the bridge is 3.5x m.
Thus, (3.5x + x)/40 - x/40 = 21
Solving, x = 240m.
Thus, length of the bridge = 3.5*240 = 840m.
10. A thief is noticed by a policeman from a distance of 400 m. The thief starts running and policeman chased him. The thief and the policeman run at the rate of 10 km and 11 km per hour respectively. What is distance between them after 12 minutes?
A. 100 m
B. 200 m
C. 150 m
D. 250 m
E. None of these
Sol. Relative speed = (11-10) = 1 km/hr
Distance covered in 12 minutes,
= 12/60
= 0.2 km.
= 200 m
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