Abstract Let fk(n):=∑dk∣nΦ(d), $$ f_k(n):=\sum\limits_{d^k \mid n} \Phi(d), $$ where Φ( d ) is a multiplicative function, Φ( d ) = O ( d ε ). We study asymptotic behaviour of the sum Tfkc(N):=∑n≤Nfknc,1<c<2, $$ T_{f_k}^c(N):=\sum\limits_{n \leq N} f_k\left(\left\lfloor n^c\right\rfloor\right), \quad 1<c<2, $$ and establish some asymptotic formulas for Tfkc(N) $ T_{f_k}^c(N) $ under assumptions on f k .