<image>In order to understand the physical condition of the senior male students in a certain school, the weights (in kg) of all 480 senior male students were measured. The data falls within the interval [50,75], and the frequency distribution histogram is shown in the figure. If the frequency ratio of the first three groups from left to right in the figure is 1:2:3, then the number of senior male students whose weight is less than 60 kg is _______ _