If 50% of a reaction occurs in 100 seconds and 75% of the reaction occurs in 200 seconds, the order of this reaction is

For first order reaction $\mathrm{K}=\frac{2.303}{\mathrm{t}}\log \left(\frac{\mathrm{a}}{\mathrm{a}-\mathrm{x}}\right)\text{ At }100\mathrm{S};\mathrm{K}=\frac{2.303}{100}\log \left(\frac{100}{100-50}\right)$
$\mathrm{K}=\frac{2.303}{100}\log 2=0.00693{\min }^{-1}\text{ At }200\mathrm{S},\mathrm{K}=\frac{2.303}{200}\log \left(\frac{100}{100-75}\right)$
$=\frac{2.303}{200}\log 4=0.00693{\min }^{-1}$
1As rate constant is same at 100 S & 200 S therefore order of reaction is 1.