John had a stock of 400 pens in his bookshop. He sold 50 on Monday, 25 on Tuesday, 80 on Wednesday, 100 on Thursday and 85 on Friday. What percentage of the pens were not sold?  Choose the correct option:
A) 15%  B) 25%  C) 86%  D) 42%  E) 55%
Let N be the total number of pens sold. Hence   N = 50 + 25+ 80 +100 + 85= 
<gadget id="calculator">50 + 25+ 80 +100 + 85</gadget>
<output>340</output>
340   Let M be the pens NOT sold   M= 400 - N = 400 - 340 = 798   Percentage   pens not sold / total number of books = 60/400= 
<gadget id="calculator">60/400</gadget>
<output>3/20 = around 0.15</output>
0.15= 15%   correct answer 15%
<result>A</result>
John had a stock of 400 pens in his bookshop. He sold 50 on Monday, 25 on Tuesday, 80 on Wednesday, 100 on Thursday and 85 on Friday. What percentage of the pens were not sold?