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.

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 ?
0.4

Your class had a pizza party . 0.375 of a pizza was left over , and 0.5 of another pizza was left over . You put them both into one box . How much pizza do you have altogether ?
0.875

At the beach , Janet and her sister both built sandcastles and then measured their heights . Janet 's sandcastle was 3.6666666666666665 feet tall and her sister 's was 2.3333333333333335 feet tall . How much taller was Janet 's sandcastle than her sister 's ?

1.3333333333333333