Sum of distance travelled in $t^{t h}$ and $(t+1)^{t h}$ seconds is $100 cm$

$u+\frac{a}{2}(2 t-1)+u+\frac{a}{2}(2(t+1)-1)=100$

$2 u+2 a t=100$

$u+a t=100 / 2$

$\Rightarrow v=50 cm / s$