A person was asked to make a guess about his own weight. He guessed that it is greater than 70 kg but less than 80 kg. His friend guessed that it more than 74 kg but less than 84 kg. His mother said that it is less than 78 kg. Given that the weight is a whole number and that all three guessed correctly, what is the average (in kg) of the possible weights?

76 kg

According to 1st person , weight is b/w 70kg to 80kg

According to 2nd  person , weight is b/w 74kg to 84kg

According to 3rd person , weight is less than 78kg 

So , Possible value of weight is 75 , 76 , 77

Desired average =  \(\frac{75 + 76 + 77 }{3}\)  = 76 kg