Management Aptitude Test 2018 Paper

(c) Raman can do a piece of work in 24 days.
∴ 1 day's work of Raman = $\frac{1}{24}$
And, 1 day's work of Kedar = $\frac{1}{12}$
[As Kedar is twice as efficient as Raman]
∴ 1 day work of both Raman and Kedar
= $\frac{1}{24}+\frac{1}{12}=\frac{3}{24}=\frac{1}{8}$
Hence, both will complete the work in 8 days.