If the average (arithmetic mean) of a and b is 50 and the average (ari

Question

If the average (arithmetic mean) of a and b is 50 and the average (arithmetic mean) of b and c is 70, what is the value of c – a ?

A. 10
B. 20
C. 40
D. 60
E. It cannot be determined from the information given.

generis · Answer

If  \frac{a + b}{2} = 50 , then
 a + b = 100 , and similarly
 c + b = 140

Subtract first equation from second equation.

c + b = 140 
 a + b = 100 
··························
 c - a = 40

Answer  C

AkshdeepS · Answer

\frac{(a + b)}{2}  = 50

a + b = 100

b = 100 - a -----> (I)

\frac{(b + c)}{2}  = 70

b + c = 140 ------> (II)

Using equation I & II we get c - a =  40 (C)

dontgiveup2020 · Answer

(a + b)/2 = 50
Hence, a + b = 100  Equation 1

(b + c)/2 = 70
Hence, b + c = 140  Equation 2

Subtract  Equation 1  from  Equation 2 :
(b + c) - (a + b) = 140 - 100
c - a = 40 (Answer C)

Prep Toolkit