You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

[EX Q]: Lucy went to the grocery store . She bought 12 packs of cookies and 16 packs of noodles . How many packs of groceries did she buy in all ?
[EX A]: 28

[EX Q]: Karin 's science class weighed plastic rings for an experiment . They found that the orange ring weighed 0.08333333333333333 ounce , the purple ring weighed 0.3333333333333333 ounce , and the white ring weighed 0.4166666666666667 ounce . What was the total weight of the plastic rings ?
[EX A]: 0.8333333333333334

[EX Q]: When Jake had 1 cat , he needed to serve 0.5 can of cat food each day . Now that Jake has adopted a second cat , he needs to serve a total of 0.9 can each day . How much extra food is needed to feed the second cat ?
[EX A]:
0.4