This letter attempts to understand the observed flattening of galaxies’ rotation-curves in terms of gravitational-pull of fast-rotating interior-stars on the slow-rotating stars at out-skirts of the galaxy. Due to fast rotation of the interior-stars, the relative-position of the stars vary at different times, adding a sinusoidal-component to the tangential-velocity of the stars at the out-skirts. These sinusoidal-components, caused by different stars in the interior, are of different frequencies, depending upon the tangential-speed of the star. The resultant sum of these sinusoidal components of different frequencies mutually nullify up to a certain radial distance, but then start adding coherently at the out-skirts; causing significant increase in the rotational velocity of the star at the out-skirts. Thus, it may not be necessary to invoke Dark-Matter, or to modify Newtonian Dynamics, as proposed in MOND or scalar-vector-theory of John Moffat.