RBI Assistant Prelims 2016-17 (Important Questions-2)
Directions (1 -5): What will come in place of (_) in the following number series ?
1. 55, 111, 221, _, 885, 1771
A. 441
B. 443
C. 442
D. 444
E. None of these
Sol. 55 + (55+1) = 111
111 + (111-1)= 221
221 + (221+1)= 443
443 + (443-1)= 885
885 + (885+1)= 1771.
2. -17, -5, 27, 99, 251, _
A. 533
B. 563
C. 555
D. 540
E. None of these
Sol. -5 -(-17) = 12
27 -(-5) = 32
99 - 27 = 72
251 - 99 = 152
563 - 251= 312
32 - 12 = 20
72 - 32 = 40
152 - 72 = 80
312 - 152= 160.
3. 16807, _, 686, 294, 168, 120
A. 2400
B. 2401
C. 2404
D. 2403
E. None of these
Sol. 16807*(1/7) = 2401
2401*(2/7) = 686
686*(3/7) = 294
294*(4/7) = 168
168*(5/7) = 120.
4. 4296, 4234, _, 4050, 3928, 3786
A. 4165
B. 4152
C. 4142
D. 4184
E. None of these
Sol. 4296 - 4234 = 62
4234 - 4152 = 82
4152 - 4050 = 102
4050 - 3928 = 122
3928 - 3786 = 142.
5. 156, 151, _, 126, 106
A. 138
B. 135
C. 132
D. 141
E. None of these
Sol. 156 - 151 = 5
151 - 141 = 10
141 - 126 = 15
126 - 106 = 20.
6. A piece of wire 72 cm long is bent successively in the shape of an equilateral triangle and a square. What is the difference between the areas of both ?
A. 235.3
B. 74.58
C. 326.6
D. 65.58
E. None of these
Sol. Length of wire = Perimeter of equilateral triangle = side*3 = 72
Side of equilateral triangle = 72/3 = 24 cm.
Length of wire = Perimeter of square = side*4 = 72
Side of square = 72/4 = 18 cm.
Area of equilateral triangle = [(24^2)*(3)^0.5]/4 = 249.42
Area of square = (18)^2 = 324
Required difference = 324 - 249.4 = 74.58.
7. There are 4 numbers. Average of first 3 numbers is 17 and of last 3 is 20. If the last number is 21, find the first number ?
A. 16
B. 15
C. 17
D. 18
E. 12
Sol. Lets assume th numbers to be a, b, c and 21.
According to the question,
(a+b+c)/3 = 17
a+b+c = 51
(b+c+21)/3 = 20
b+c = 39.
Thus, a + 39 = 51
a = 51 - 39 = 12.
8. The sum of a 2-digit is 13. When 27 is added to the number , the digits of the number are reversed. What is the actual number ?
A. 57
B. 58
C. 98
D. 60
E. None of these
Sol. Lets assume ten's digit be 'x' and unit's digit be (13 - x)
Then number = 10x + (13-x) = 9x + 13
Digit with reversed digits = 10(13-x) + x = 130 - 9x
According to the question,
9x + 13 + 27 = 130 - 9x
x = 5.
Therefore, the required number = 9*5 + 13 = 58.
9. The breadth of the rectangular park is 3/4th of its length. If the area of the park is 1200 sq.m. then the difference between its length and breadth is ?
A. 3
B. 10
C. 5
D. 15
E. 20
Sol. Let the length be 'l'
Then breadth will be '3l/4'
According to the question,
l*3l/4 = 1200
Thus, l = 40.
Length = 40
Breadth = 3*40/4 = 30
Therefore, required difference = 40 - 30 = 10.
10. The population of a town 2 years ago was 245000. It increased by 15% in first year and increased 20% in second year. What is the current population of the town ?
A. 338100
B. 274400
C. 351560
D. 294400
E. None of these
Sol. Population after 1st year = 115*245000/100 = 281750
Population after 2nd year = 120*281750/100 = 338100.
Directions (1 -5): What will come in place of (_) in the following number series ?
1. 55, 111, 221, _, 885, 1771
A. 441
B. 443
C. 442
D. 444
E. None of these
Sol. 55 + (55+1) = 111
111 + (111-1)= 221
221 + (221+1)= 443
443 + (443-1)= 885
885 + (885+1)= 1771.
2. -17, -5, 27, 99, 251, _
A. 533
B. 563
C. 555
D. 540
E. None of these
Sol. -5 -(-17) = 12
27 -(-5) = 32
99 - 27 = 72
251 - 99 = 152
563 - 251= 312
32 - 12 = 20
72 - 32 = 40
152 - 72 = 80
312 - 152= 160.
3. 16807, _, 686, 294, 168, 120
A. 2400
B. 2401
C. 2404
D. 2403
E. None of these
Sol. 16807*(1/7) = 2401
2401*(2/7) = 686
686*(3/7) = 294
294*(4/7) = 168
168*(5/7) = 120.
4. 4296, 4234, _, 4050, 3928, 3786
A. 4165
B. 4152
C. 4142
D. 4184
E. None of these
Sol. 4296 - 4234 = 62
4234 - 4152 = 82
4152 - 4050 = 102
4050 - 3928 = 122
3928 - 3786 = 142.
5. 156, 151, _, 126, 106
A. 138
B. 135
C. 132
D. 141
E. None of these
Sol. 156 - 151 = 5
151 - 141 = 10
141 - 126 = 15
126 - 106 = 20.
6. A piece of wire 72 cm long is bent successively in the shape of an equilateral triangle and a square. What is the difference between the areas of both ?
A. 235.3
B. 74.58
C. 326.6
D. 65.58
E. None of these
Sol. Length of wire = Perimeter of equilateral triangle = side*3 = 72
Side of equilateral triangle = 72/3 = 24 cm.
Length of wire = Perimeter of square = side*4 = 72
Side of square = 72/4 = 18 cm.
Area of equilateral triangle = [(24^2)*(3)^0.5]/4 = 249.42
Area of square = (18)^2 = 324
Required difference = 324 - 249.4 = 74.58.
7. There are 4 numbers. Average of first 3 numbers is 17 and of last 3 is 20. If the last number is 21, find the first number ?
A. 16
B. 15
C. 17
D. 18
E. 12
Sol. Lets assume th numbers to be a, b, c and 21.
According to the question,
(a+b+c)/3 = 17
a+b+c = 51
(b+c+21)/3 = 20
b+c = 39.
Thus, a + 39 = 51
a = 51 - 39 = 12.
8. The sum of a 2-digit is 13. When 27 is added to the number , the digits of the number are reversed. What is the actual number ?
A. 57
B. 58
C. 98
D. 60
E. None of these
Sol. Lets assume ten's digit be 'x' and unit's digit be (13 - x)
Then number = 10x + (13-x) = 9x + 13
Digit with reversed digits = 10(13-x) + x = 130 - 9x
According to the question,
9x + 13 + 27 = 130 - 9x
x = 5.
Therefore, the required number = 9*5 + 13 = 58.
9. The breadth of the rectangular park is 3/4th of its length. If the area of the park is 1200 sq.m. then the difference between its length and breadth is ?
A. 3
B. 10
C. 5
D. 15
E. 20
Sol. Let the length be 'l'
Then breadth will be '3l/4'
According to the question,
l*3l/4 = 1200
Thus, l = 40.
Length = 40
Breadth = 3*40/4 = 30
Therefore, required difference = 40 - 30 = 10.
10. The population of a town 2 years ago was 245000. It increased by 15% in first year and increased 20% in second year. What is the current population of the town ?
A. 338100
B. 274400
C. 351560
D. 294400
E. None of these
Sol. Population after 1st year = 115*245000/100 = 281750
Population after 2nd year = 120*281750/100 = 338100.
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