Latest Infosys Aptitude Question SOLUTION: l.c.m & h.c.f of two numbers is 84 & 21 respectively and the ratio of these two numbers is 1:4. Find the greatest no…

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l.c.m & h.c.f of two numbers is 84 & 21 respectively and the ratio of these two numbers is 1:4. Find the greatest no…

Asked In Infosys sawan kumar (12 years ago)

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Dr.Dipin Singh  (12 years ago)

84.

If nos are x and 4 x, then
x*4x= 84*21
x^2=21*21
x=21
4x=84

Is this solution Helpfull? Yes (8) | No (3)  

sacreties  (12 years ago)

let the numbers be X,Y
given that X/Y=1/4 ,by cross multiplying we get 4X=Y------eq(1)
we know that,
product of two numbers= product of their H.C.F&L.C.M
so XY=84*21=1764---------eq(2)
substitute eq(1) in eq(2)
4(X^2)=1764
X^2=441
so X=21
substitute X value in eq(1) we get Y=84
so 84 is the greatest number

Is this solution Helpfull? Yes (4) | No (3)  

keerthana v  (9 years ago)

we have a formula:
=>LCM*HCF=Product of 2 numbers
We are given that 2 numbers are in the ratio 1:4. So let the numbers be x and 4x. Substitute in the above formula to get the value of x.
=>84*21=x*4x
Solving the above equation we get the value of x as 21.
So the two numbers are x and 4x.
Therefore greatest number is 4x=4*21=84.
Thank u.
Hope this is useful

Is this solution Helpfull? Yes (2) | No   

Nithiya  (5 years ago)

x*4x=21*84
4x^2=21*84
x^2=21*84/4
x=21
4(x)=>4(21)=84
ans is 84

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  (4 years ago)

l.c.m*h.c.f=product of 2 numbers
84*21=x*y
x/y=1/4->4x=y
4x^2=84*21
x=21
y=4*21=84

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