Question

In a class of 80 students, 60% are girls and the rest are boys. The average weight of boys is 5% more than that of girls. If the average weight of all the students is 51 kg, then what is the average weight (in kg) of the boys?  

पर्याय

• 55

• 47.5

• 52.5

• 50

Answer 1

52.5

Explanation:

Total students = 80

No. of girls = `3/5 xx 80`

= 48

Now, no. of boys = (80 − 48)

= 32

Average weight of all students = 51 kg

∴ Total weight = [51 x 80] kg

= 4080 kg

Now, Avg. of boys = `21/20` × The Average weight of girls

Let the average weight of girls be 'b'

∴ The average weight of boys

The average weight of al I students = 51 kg

Now, 51 kg = `((32 xx b+2 "lb")/(20 xx 48))/ 80`

⇒ 4080 × 5 = 160b + 252b

⇒ ~ b = 49.51

∴ Avg. weight of boys = `21/20 xx 49.51`

= 52.5kgs