Mathmetics

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

Q11.
What is value of the given sequence (53 + 63 + 73+…….. + 103) ?
1) 2295 2) 2425
3) 2595 4) 2925
5)None of these
Answer : 2925
Explanation : We know that , the sum of the cube all natural number i.e. 1- n = [(n. n+1)/2]2

The sequence is  (13 + 23+ 33 + 43+  …….. + 103) -  (13 + 23+ 33 + 43)

So, [(10 x 11)/2]2 - [(4x5)/2]2 = 3025 -100 = 2925

View Answer

Q12.
The sum of the squares of two numbers is 68 and the square of their difference is 36. what is the product of the two numbers ?
1) 16 2) 52
3) 58 4) 104
5)None of these
Answer : 52
Explanation : Let, two  numbers are x and y respectively. 
So, x2 + y2 = 68 and ( x - y )2 = 36.
We know that, ( x - y )2 = x2 + y2 - 2xy  
or 68 - 2xy = 36
or 2xy = 68+36 = 104
or xy = 104/2=52

View Answer

Q13.
If doubling a number and adding 20 to the result gives the same answer as multiplying the number by 8 and taking away 4 from the product, then what is the number ? 
1) 2 2) 3
3) 4 4) 5
5)None of these
Answer : 3
Explanation : Let, the number be x.
2x + 20 = 8x - 4
or 8x - 2x  = 20 + 4 = 24
or 6x =24
or x= 24/6= 4
View Answer

Q14.
Three-fourth of two-third of 240 is added to two-third of a number, the resultant number is 360. What is value of the original number ?
1) 180 2) 240
3) 320 4) 360
5)None of these
Answer : 360
Explanation : Given , 3/4 x 2/3 x 240 +2x/3 = 360
or 120 + 2x/3 = 360
or x = 360
View Answer