$\mathrm{Convert} \frac{10}{25} \mathrm{into} \mathrm{percentage}$

When converting fraction into percentage, we have to obtain the denominator of 100. When multiplying 25 by 4, we get 100. And to keep the fraction equal, we have to multiple 10 by 4, we get 40.

Hence $\frac{10*4}{25*4}=\frac{40}{100}$

Hence 40%