DRDO Multi tasking staff Model paper 8

Let the weights (in kg) of top 5 students be x1,x2,x3,x4‌and‌x5 respectively.
Average weight of the top two students =x1+1.5
(∵ average weight increases by one and a half kg each time)
⇒(x+x2)/2=x1+1.5
⇒x2=x1+3
Similarly,
x3=x1+6,x4=x1+9‌and‌x5=x1+12
∴ The last student is heavier than the first student by 12 kg.