Question

If average of a and b is 20, average of b and C is 30 and average of a and c is 70. What is the
average of a, b and c?

Answer 1

Answer:

20

Step-by-step explanation:

Step 1:

Average of A and B is 30 What is the value of C-A?

(A+B)/2 = 30

A+B = 60 —(1)

and the average of B and C is 40,

(B+C)/2 = 40

B+C = 80 —(2)

What is the value of C-A?

Step 2:

solve equation (1) and (2)

A+B = 60

B+C=80

A-C = -20

ie.

C-A = 20

PLZ MARK IT AS A BRAINLIST ANSWER .

Answer 2

Answer:

A = 60

B = -20

C = 140

Average = 60

Step-by-step explanation:

Average of A and B = $\frac{ A + B}{2}$ = 20 (1)

-> A + B = 40

Average of B and C = $\frac{B + C}{2}$ = 30 (2)

-> B + C = 60

Average of A and C = $\frac{C + A}{2}$ = 70 (3)

-> A + C = 140

Adding (2) and (3):

$\frac{C + B}{2}$ + $\frac{A + C}{2}$ = $\frac{A + B + 2C}{2}$ = 30 + 70 = 100 (4)

Subtracting (1) from (4):

$\frac{A + B + 2C}{2}$ - $\frac{A + B}{2}$ = $\frac{2C}{2}$ = C = 100 - 20 = 80

Since A + C = 140,

A = 140 - 80 = 60

B = 40 - 60 = -20

Therefore:

A = 60

B = -20

C = 140

Average = $\frac{60 + 140 - 20}{3}$ = 180/3  = 60