Question

The average marks of 28 students in Mathematics was 50.8 students left the school, then this average increased by 5. What is the average of marks obtained by the students who left the school?​

Answer 1

AnswEr :

$\bold{Given} \begin{cases}\sf{Students=28}\\ \sf{Average=50}\end{cases}$

$\bold{New\:Data}\begin{cases}\sf{Students=(28-8)=20} \\ \sf{Average=(50+5)=55}\end{cases}$

$\bold{To\:Find}\begin{cases}\sf{Left \:Students=8} \\ \sf{Average=?}\end{cases}$

• Let's Head to the Question Now :

$\implies \tt \underbrace{Total}_{Students\times Average} = \underbrace{New}_{Students \times Average} + \underbrace{Left}_{Students \times Average}$

$\implies \tt(28 \times 50) = (20 \times 55) + (8\times Average)$

$\implies \tt1400 =1100+ (8\times Average)$

$\implies \tt1400 - 1100 = 8\times Average$

$\implies \tt300= 8\times Average$

$\implies \tt \cancel\dfrac{300}{8} = Average$

$\implies \large\boxed{\tt Average = 37.5}$

⠀

∴ Average Marks of left students is 37.5

Answer 2

${\bold{\underline{\boxed{Answer = 37.5}}}}$

$\Large\underline{\underline{\sf \blue{Given :}}}$

Number of students = 28

Average Marks of 28 students in maths = 50

StEp-bY-sTeP-ExPlANatiON :

$\implies$ The average of marks of 28 students in Mathematics = 50

$\implies$ So, Total marks of the 28 students = 28 × 50 = 1400

$\implies$ Also, When 8 students left , The average of marks of 20 students = 55

$\implies$ Total marks of 20 students = 20 × 55 = 1100

$\implies$ $\therefore$ Total marks of 8 students = 1400 – 1100 = 300

$\longrightarrow$ $\therefore$ Average = 300 ÷ 8 = 37.5