title: Excel Vlookup calculating grades with mark range
body: <p>I am new to excel and i would like to use a function called vlookup to calculate some grades according to a table.
  However i failed to do so which i do not know where i did wrong in the formula. 
  can anyone point me out to a solution please? Thank you so much~</p>
  
  <p>The link below will be the image of my the excel.
  <a href="http://postimg.org/image/n26gxaxpx/" rel="nofollow">http://postimg.org/image/n26gxaxpx/</a></p>