Question

The average of 7 results is 50 , that of the first 3 is 55 and that of the last of 3 is 48. The value of the 4th number is​

Answer 1

total of 7 result is = 7×50 = 350

total of first 3 result is 3×55= 165

total of last 3 result is 3×48 = 144

4 th value = total of 7 result - ( total of first 3+total of last 3)

350-(165+144) = 350-309 = 41

Answer 2

Given sin(A+B)=1

⇒sin(A+B)=sin90

o

(∵sin90

o

=1)

⇒A+B=90

o

…………(1)

Again, cos(A−B)=

3

/2

⇒cos(A−B)=cos30

o

(∵cos30

o

=

3

/2)

⇒A−B=30

o

…………(2)

Adding (1)+(2)

A+B+A−B=90

o

+30

o

⇒2A=120

⇒A=120/2

⇒A=60

Putting A=60

in equation-(2) we get

A−B=30

⇒60

−B=30

⇒60

−30

=B

⇒B=30

∴A=60

;B=30