Question

q.4 a plz solve it jaldi​

Answer 1

Answer:

6+a+16+13+b=40

a+b=5

Mean=7.2=(30+6a+112+104+9b)/40

7.2=(246+6a+9b)/40

288=246+6a+9b

6a+9b=42

2a+3b=14

2a+2b=10

2a+3b-2a-2b=4

b=4

a=1

Answer 2

Answer:

The value of a and b are 1 and 4 respectively.

Step-by-step explanation:

There are 40 students in the class.

$6+a+16+13+b=40\\a+b=5...(i)$

The mean marks is 7.2.

The formula of mean is:

$Mean=\frac{1}{N} \sum f_{i}x_{i}$

$\frac{1}{40}[(5\times6)+(6\times a)+(7\times16)+(8\times 13)+(9\times b)]=7.2\\ 30+6a+112+104+9b=288\\6a+9b=42\\2a+3b=14...(ii)$

Solve equations (i) and (ii) simultaneously as follows:

Multiply (i) by 3 and subtract:

$3a+3b=15\\-2a-3b=-14\\\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\\a=1$

Substitute a = 1 in (i) and compute b as follows:

$a+b=5\\1+b=5\\b=4$

Thus, the value of a and b are 1 and 4 respectively.