Find first and third quartiles from the following distributin.

Explanation

`Q_(1)=N/4"th item"=80/4"th item"=20"th item"`
`Q_(1)"calss"=20-40`
`sumf_(1)=8,f_(Q1)=17,l_(1)=20,i=20`
`Q_(1)=l_(1)+(((N)/(4)-sumf_(1))/(f_(Q1)))i=20+((20-8)/(17))xx20=20+(12xx20)/(17)`
`=20+(240)/(17)=20+14.12`
= 34.12 marks approx,
= 34. 12 marks approx,
`Q_(3)=(3N)/(4)"th itme"=(3xx80)/(4)"th item"=60"th item"`
`Q_(3)"calss" = 60-80`
`sumf_(1)=52,f_(Q3)=18l_(1)=60,i=20`
`Q_(3)=l_(1)=+(((3N)/(4)-sumf_(1))/(f_(Q1)))xxi=60+((60-52)/(18))xx20`
`=60+(8xx20)/(18)=60+((60-52)/(18))xx20`
`=60+(8xx20)/(18)=60+(160)/(18)=60+8.89`
= 68.89 marks approx.