Question

if y is directly proportional to 1/x and x=2 when y=20,what is the value of x when y=1.25

Answer 1

Y is directly proportional to 1/x

Xy= k (where k is constant)

So, for x= 2 and y=20

K=xy

K=2×20

K= 40. -(1)

Now,
For y= 1.25

K= 1.25x. -(2)

From equation 1 and 2

40=1.25x

X= 40/1.25
= 32.

Hope it helps

Answer 2

Since, y is directly proportional to 1/x
y = k*1/x (where k is constant of proportionality)
so,
For x = 2 and y = 20
=> k = xy
=> k = 2*20
=> k = 40. -----(1)
Now, for y = 1.25
=> k = xy
=> k = x*1.25
=> k = 1.25x. -------(2)
from equation (1) & (2)
=> 40 = 1.25x
=> 40/1.25 = x
Therefore, x = 32 (answer)


Hope it helps you.
Thank you.