  We consider one dimensional interacting bose-fermi mixture with equal masses
of bosons and fermions, and with equal and repulsive interactions between
bose-fermi and bose-bose particles. Such a system can be realized in current
experiments with ultracold bose-fermi mixtures.We apply the Bethe-ansatz
technique to find the exact ground state energy at zero temperature for any
value of interaction strength and density ratio between bosons and fermions. We
use it to prove the absence of the demixing, contrary to prediction of a mean
field approximation. Combining exact solution with local density approximation
(LDA) in a harmonic trap, we calculate the density profiles and frequencies of
collective modes in various limits. In the strongly interacting regime, we
predict the appearance of low-lying collective oscillations which correspond to
the counterflow of the two species. In the strongly interacting regime we use
exact wavefunction to calculate the single particle correlation functions for
bosons and fermions at low temperatures under periodic boundary conditions. We
derive an analytical formula, which allows to calculate correlation functions
at all distances numerically for a polynomial time in the system size. We
investigate numerically two strong singularities of the momentum distribution
for fermions at $k_f$ and $k_f+2k_b.$ We show, that in strongly interacting
regime correlation functions change dramatically as temperature changes from 0
to a small temperature $\sim E_f/\gamma.$ A strong change of the momentum
distribution in a small range of temperatures can be used to perform a
thermometry at very small temperatures.
