###Human: Mark goes into the store to buy some groceries.  He buys 6 2$ cans of soup, 2 $5 loaves of bread, 2 3$ boxes of cereal, and 2 $4 gallons of milk.  When he gets to the register, he opens his wallet to pay and realizes he only has $10 bills in there.  How many $10 bills does he need to use to pay?, ### Assistant: Mark buys 6 $2 cans of soup, meaning he spends 6*2= 12 dollars on soup.
Mark buys 2 $5 loaves of bread, meaning he spends 2*5= 10 dollars on bread.
Mark buys 2 $3 boxes of cereal, meaning he spends 2*3= 6 dollars on cereal.
Mark buys 2 $4 gallons of milk, meaning he spends 2*4= 8 dollars on milk.
All added together, this means Mark spends 12+10+6+8= 36 dollars
Since Mark only has $10 bills, he spends 36/10= 3.6 tens on it, which rounds up to 4 as you cannot spend .6 of an undividable item. 
 So the answer is :  4