In what time will Rs 1000 amount to Rs 1331 at 10% per annum,

Let the time be $\mathrm{n}$ years.

Then,

$\mathrm{A}=\mathrm{P}\left(1+\frac{10}{100}\right)^{\mathrm{n}}$

$1,331=1,000\left(1+\frac{10}{100}\right)^{\mathrm{n}}$

$(1.1)^{\mathrm{n}}=\frac{1,331}{1,000}$

$(1.1)^{\mathrm{n}}=1.331$

$(1.1)^{\mathrm{n}}=(1.1)^{3}$

On comparing both the sides, we get:

n = 3

Thus, the required time is three years.