Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q21. 

1)  1/3  2)  1/4 
3)  1/2  4)  No change 
5)  None of these 
Answer : 1/2
Explanation :
Explanation :
Let the length and breadth of the rectangle be L and B respectively.
Area = L x B = LB
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Q22.  If (1^{3}+2^{3}+3^{3}+4^{3}+ 5^{3}+6^{3}+................+10^{3}) = 3025 ,then find the value of (2^{3}+4^{3}+6^{3}+8^{3}+ 10^{3}+...............+20^{3}) 
1)  6050  2)  10060 
3)  12040  4)  24200 
5)  None of these 
Answer : 24200
Explanation : We can express , (2^{3}+4^{3}+6^{3}+8^{3}+ 10^{3}+...............+20^{3}) =
Explanation : We can express , (2^{3}+4^{3}+6^{3}+8^{3}+ 10^{3}+...............+20^{3}) =
2^{3} x (1^{3}+2^{3}+3^{3}+4^{3}+ 5^{3}+6^{3}+................+10^{3}) = 8 x 3025 = 24200
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Q23.  Given that, (1^{2}+2^{2}+3^{2}+4^{2}+ 5^{2}+6^{2}+7^{2}) = x +1 , the find the value of the following expressions: 
1)  2(x+1)  2)  4(x+1) 
3)  8(x+2)  4)  16(x+1) 
5)  None of these 
Answer : 4(x+1)
Explanation : We can write, (2^{2}+4^{2}+6^{2}+8^{2}+10^{2}+12^{2}+ 14^{2}) = 2^{2} x (1^{2}+2^{2}+3^{2}+4^{2}+ 5^{2}+6^{2}+7^{2}) = 4(x+1)
Explanation : We can write, (2^{2}+4^{2}+6^{2}+8^{2}+10^{2}+12^{2}+ 14^{2}) = 2^{2} x (1^{2}+2^{2}+3^{2}+4^{2}+ 5^{2}+6^{2}+7^{2}) = 4(x+1)
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Q24. 

1)  25  2)  36 
3)  38  4)  30 
5)  None of these 
Answer : 36
Explanation :
Explanation :
The smallest angle = 3/15 x 180° = 36°
The largest angle =7/15 x 180° = 84°
So, (36 x 2)  (84/ 2) = 36
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Q25. 

1)  30 yrs  2)  24 yrs 
3)  18 yrs  4)  36 yrs 
5)  None of these 
Answer : 30 yrs
Explanation : The present age of C = 72  42 = 30 years
Explanation : The present age of C = 72  42 = 30 years
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Q26. 

1)  344.35 cm2  2)  462 cm2 
3)  498.35 cm2  4)  456cm2 
5)  None of these 
Answer : 498.35 cm2
Explanation :
Explanation :
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Q27.  A tank has three drain pipes, the first two pipes A and B operating simultaneously can empty the tank in half the time that of C, third pipe, alone takes to empty it. Pipe A working alone takes half the time taken by pipe B. Together they take to fill the tank in 6 hrs 40 mins. What is time taken for A to empty the tank alone ? 
1)  11hrs  2)  12 hrs 
3)  111/9hrs  4)  121/3hrs 
5)  None of these 
Answer : 111/9hrs
Explanation :
Explanation :
Let, C pipe takes x hrs ,then A pipe takes x/2 hrs
So, C pipe takes
=2(x+x/2) =3x hrs
Then, (A+B+C) pipes can
do in 1 hr = 1/x + 2/x +1/3x = 10/3x hrs
But given , total
time taken by all pipes = 6 hrs 40 min =
62/3 hrs = 20/3 hrs
So, 10/3x hrs = 3/20
Or x =200/9 hrs i.e time
taken for pipe B
Therefore, time taken
for pipe A = (200/9)/2 = 100/9 = 111/9hrs
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Q28. 

1)  18.8 cm  2)  23.5 cm 
3)  24 cm  4)  31.3cm 
5)  None of these 
Answer : 24 cm
Explanation :
Explanation :
The final ratio of the triangle are 20 : 15 : 12
Perimeter = 20x + 15x + 12x = 47 x
So, 47x = 94
or = x = 2
Thus smallest side = 122 = 24 cm.
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Q29. 

1)  16 cm  2)  18 cm 
3)  24 cm  4)  Data Inadequate 
5)  None of these 
Answer : 18 cm
Explanation :
Explanation :
2(l + b) /b = 5/1 or 2l + 2b = 5b
or 3b = 2l b =2l/3
Then, Area = 216 cm2
l x b = 216
l x2l/3 = 216 or l^{2 }= 324
or l = 18 cm.
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Q30. 

1)  15 mtrs  2)  26 mtrs 
3)  25 mtrs  4)  20 mtrs 
5)  None of these 
Answer : 20 mtrs
Explanation :
Explanation :
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