1.
d = {'Physics':82,'Maths':65,"history":75}
m = float('inf')
ans = ""
for k,v in d.items():
if(v<m):
m = v
ans = k
print(ans)

2.
s = {'a':100,'b':200,'c':300}
found = False
for k,v in s.items():
if(v==200):
found = True
if found:
print("200 present in a dict.")
else:
print("200 not present in a dict.")

3.

dict1 = {'Ten':10,'Twenty':20,'Thirty':30}
dict2 = {'Thirty':30,'Forty':40,'Fifty':50}
dict1.update(dict2)
print(dict1)