Correct Answer - Option 3 : 20

**Given:**

The mean weight of 100 students is 46 kg

The mean weight of boys is 50 kg

The mean weight of girls is 40 kg

**Formula used:**

Mean = Sum of total observations/Number of observations

**Calculations:**

Let the number of boys and girls be x and (100 - x)

According to the question, we have

Mean = {50x + 40(100 - x)}/100

⇒ 46 = {50x + 40(100 - x)}/100

⇒ 4600 = 50x + 4000 - 40x

⇒ 4600 - 4000 = 10x

⇒ x = 600/10

⇒ x = 60

So, The number of boys is 60

Hence, The number of girls is

Number of girls = 100 - x

⇒ Number of girls = 100 - 60

⇒ Number of girls = 40

The number of boys exceeds that the number of girls by

⇒ Difference = 60 - 40

⇒ Difference = 20

**∴ The number of boys exceeds that the number of girls by 20.**