we are given
One serving of watermelon weigh about 150 grams
watermelon required by one person =150 g
total number of persons =60
total amount of watermelon = total number of persons*watermelon required by one person
total amount of watermelon=

total amount of watermelon=

we know that

we can write as
total amount of watermelon=

we can replace 1000g as 1kg
total amount of watermelon=
...........Answer