k, k^2, k^3, 8 are four proportional numbers, then k will be

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18 Oct 2011 proportion

k, k^2, k^3, 8 are four proportional numbers, then k will be

OPtion

1) 8^(3/4)
2) 4^(3/4)
3) 2^(3/4)
4) 8
5) 4
6) 2
7) 1
8) 8^(1/2)
9) 2^(1/2)
10) none of these

Solution

According to the given condition k^2/k = 8/k^3
or k = 8/k^3
or k^4 = 8
or k = 8^(1/4)
or k = 2^(3/4)

Correct Option: 3 Best Solution (27)

Dimple   12 years AGO

k, k^2, k^3, 8 are four proportional numbers,
or
k: k^2 :: k^3 : 8
so
k*8= k^2 * k^3
k^4=8 = 2^3

Taking fourth root of both sides

k= 2^ ( 3/4) .. option 3

Like? Yes (5) | No   

Bawa   12 years AGO

k, k^2, k^3, 8 are four proportional numbers,

Ratio of first two numbers = ratio of last two numbers
k^2/k = 8/k^3
8=k^4
k= 8^(1/4) = 2^(3/4)

Like? Yes (2) | No   

Mayur   12 years AGO

k, k^2, k^3, 8 are four proportional numbers, then k will be 8^(1/4) = 2^(3/4).

Like? Yes (2) | No   

Prerna   12 years AGO

k: k^2 :: k^3: 8
hence
k*8= k^2 * k^3
8= k^4
k^4= 2^3
k = 2^(3/4)

Like? Yes (2) | No   

Arneet   12 years AGO

k, k^2, k^3, 8 are four proportional numbers,
hence k^4 should be equal to 8.
then
k = 8^(1/4) = 2^(3/4)

Like? Yes (2) | No   

Pargat Pal Singh   12 years AGO

k, k^2, k^3, 8 are four proportional numbers,
or
k, k^2, k^3, k^4 are four proportional numbers,

Hence k^4=8 = 2^3
k = 2^(3/4)
So option 3.

Like? Yes (2) | No   

rohit kumar   12 years AGO

(k/k^2)::(k^3/8)
simplifying this we get : k^4-8=0
or k=8^(1/4); or
k=2^(3/4)

Like? Yes (2) | No   

MP    12 years AGO

k^2/k = 8/k^3
k= 8/k^3
k^4=8=2^3
k= 2^(3/4)

which is option 3.

Like? Yes (1) | No   

Raja badam   12 years AGO

K:K^2::K^3:8
K^5=8K
K^4=8
K=2^(3/4)

Like? Yes (1) | No   

Dr.Dipin Singh   12 years AGO

k, k^2, k^3, 8 are four proportional numbers,

hence
k^5 = 8k
k^4=8= 2^3
k = 2^(3/4) .. option 3.

Like? Yes (2) | No (1)  

shruti   12 years AGO

2^(1*3/4), 2^(2*3/4), 2^(3*3/4), 2^(4*3/4) i.e. 8, therefore, k=2^(3/4)

Like? Yes (1) | No   

srilatha   12 years AGO

k,k^2,k^3,8
then 8k=k^(2+3)
8k=k^5
k^4=8
so the ans is k=2^(3/4)

Like? Yes (1) | No   

uma   12 years AGO

k,k^2,k^3,8
----->AD=BC
so 8k=k^5
k=2^(3/4)

Like? Yes (1) | No   

geetha   12 years AGO

(2^3/4)^4=8,so option 3

Like? Yes (1) | No   

surendran   12 years AGO

k^4=8=2^3
k^(4/3)=2
so k=2(3/4)

Like? Yes (1) | No   

Abhishek Divakar   12 years AGO

k/k^2 = k^3/8
then
k^4 = 2^3
k = 2^(3/4)

Like? Yes (1) | No   

Soumi Dutta   12 years AGO

since proportional,so,k/k^2=k^3/8
solving it comes,k=8^(1/4)=(2*2*2)^(1/4)
=((2*2*2*2)^(1/4))/2^(1/4)=2^(1-(1/4))=2^(3/4)

Like? Yes (1) | No   

Amit Kumar   12 years AGO

k^3/k^2 = k
so since the numbers are proportional
therefore
8/k^3 should be equal to k
which means k^4 = 8
therefore k = 2^(3/4)

Like? Yes (1) | No   

sivakumar   12 years AGO

8/K^3=K^3/K^2; 8=K^4; K=(8)^1/4; K=(2)^3/4;
SO THE OPTION IS 3

Like? Yes (1) | No   

Indranil Dey   12 years AGO

k:k^2::k^3:8
k:k^2=k^3:8
1:k^4=1:8
k^4=8
k^4=2^3
k=2^(3/4)

Like? Yes (1) | No   

vishal jhalani   12 years AGO

k/k^2=K^3/8;
k^4=8
K=2^3/4

Like? Yes (1) | No   

ramesh singh   12 years AGO

answer is 3)= 2^(3/4)
2^(3/4)=2^(3/4)
2^(6/4)=2*(2^(2/4)
2^(9/4)=4*(2^(1/4)
2^(12/4)= 8

Like? Yes (1) | No   

rk   12 years AGO

answer 3 i.e 2^3/4

k/k^2=k^3/8
k^4=8
k=8^1/4 or 2^3/4

Like? Yes (1) | No   

Abhishek Varshney   12 years AGO

let k=2^(3/4);
then k^2=(2^(3/4))^2=2^(6/4) and
k^3=(2^(3/4))^3=2^(9/4) and

k^4=(2^(3/4))^4=2^(12/4)=2^3= 8
k^4=8

Like? Yes (1) | No   

Milind kailas Narkhede   12 years AGO

a:b:c:d then we can write (a:b)=(c:d)=(a:d) ...........after solving of any two proportion then we easly get the ans....

Like? Yes (1) | No   

Rishi Prakash   12 years AGO

In proportion,
K/K^2=K^3/8,
so,K^4=8
K=(8)^(1/4)
K=(2)^(3/4)

Like? Yes (1) | No   

sabarish   12 years AGO

k, k^2,k^3,8 are in fourth proportional then

For porportionals; the product of the internal terms equals the product of the externals; therefore for
=> k:k^2 = k^3:8
=> 8*k = k^5
=> 8 = k^4
=> k = 8^(1/4)

=> k = 2^(3/4)

Like? Yes (2) | No (1)