when often do we need a bar graph ??
It depends upon you that you have to show it in statements or in a bar graph. It depends upon your idea that in which way you can show your information in neat 'n clean way, in simple words, in the best way. According to me, you should use statement way in long questions like how many people traveled during this,this,this and this year if there were large amount of people. And bar graph way in short questions as it is a very time taking process (when you have to simply draw the bar graph without using a bar graph paper) like drawing lines,making equal columns,etc.