Ans 1: (C) 16 years
Solution: Let 1 year before their ages were 4x and 3x
Now their ages are 4x+1 and 3x +1
After 1 year, their ages will be 4x+2 and 3x +2
Given : (4x+2)/(3x+2)=5/4
4(4x+2)=5(3x+2)
16x + 8= 15 x+ 10
16x-15x=10-8
x=2
present ages: 4x+1 and 3x+1 are (4(2) +1 ) and (3(2) +1) i.e 9 and 7
sum of their ages is 16
Ans 2: (A) 5%
Solution: Sum doubles means interest=amount
interest=p=(p*t*r)/100
r*t=100
r*20=100
r=100/20
r=5
Ans 3: (D) 49cm
Solution: Diameter=2r
circumference=2*pi*r
given diameter=circumference-105
2r=2*pi*r-105
2*pi*r-2r=105
2r(pi-1)=105
2r(22/7-1)=105
2r(15/7)=105
2r=(105*7)/15
2r=7*7
2r=49
So diameter=49
Ans 4: (D) 35
Solution: The number leaves same reaminder 7 in each case
so subtract 7 from each number
So the numbrers are 70,140 and 245
Now We have to find HCF/GCD of these 3 numbers., i.e. the greatest number, which divides all the 3 numbers.
So either find HCF/GCD by calculating or just analyse given options.
In the given options 45 does not divide 70. so no need to check any other number.
35 divides 70, 140 and 245.
So 35 is correct answer.
Ans 5: (D)
The dissolved oxygen of the groundwater escapes into air
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