C1:

\(\left(\dfrac{2}{5}+\dfrac{1}{2}\right)\times\dfrac{1}{4}=\dfrac{9}{10}\times\dfrac{1}{4}=\dfrac{9}{40}\)

C2:

\(\left(\dfrac{2}{5}+\dfrac{1}{2}\right)\times\dfrac{1}{4}=\dfrac{2}{5}\times\dfrac{1}{4}+\dfrac{1}{2}\times\dfrac{1}{4}=\dfrac{1}{10}+\dfrac{1}{8}=\dfrac{9}{40}\)