If the average (arithmetic mean) of b and c is 5, and the average of c

Question

If the average (arithmetic mean) of b and c is 5, and the average of c and d is 10, then b - d =

A. Cannot be determined
B. -5
C. -10
D. -15
E. -20

Chethan92 · Answer

(b+c)/2 = 5.
b+c = 10.....(1)
Also given that (c+d)/2 = 10
c+d = 20.....(2)

Subtract 1 from 2 gives b-d = 10-20 = -10.

C is the answer

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KSBGC · Answer

\frac{b + c}{2} = 5

b + c = 10......................................equation 1

again,

\frac{c + d}{2} = 10

c + d = 20.......................................equation 2.

deduct 2 from 1 :

(b + c) - (c + d) = b +c - c - d = b -d

10 - 20 = b- d

b - d = -10.

The best answer is C.

CounterSniper · Answer

b+c=10 ------1
c+d=20 ------2

subtracting 1 from 2
b-d= -10

ScottTargetTestPrep · Answer

We can create the equations:

(b + c)/2 = 5

b + c = 10

and

(c + d)/2 = 10

c + d = 20

Subtracting the second equation from the first we have:

b - d = -10

Answer: C

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