Bunuel wrote:

If Janice was 25 years old z years ago and Lisa will be 23 years old in p years, what was the average (arithmetic mean) of their ages 5 years ago?

A. (48 + z - p)/2

B. (38 - z + p)/2

C. (38 + z + p)/2

D. (38 + z - p)/2

E. (48 + z + p)/2

Assign values that make the equations easy.

Let Janice = 30 now, z years ago she was 25

z = 5

Let Lisa = 20 now, in p years she will be 23

p = 3

Average of their ages 5 years ago? Five years ago

Janice: (30 - 5) = 25

Lisa: (20 - 5) = 15

Average 5 yrs ago \(\frac{25+15}{2}=20\)

All the answers are divided by 2.

With

z = 5, p = 3, find the answer with a

numerator of 40, because 40/2 = 20 = average of their ages

A. (48 + z - p)/2

48 + 5 - 3 =

50 NOT A MATCH

B. (38 - z + p)/2

38 - 5 + 3 =

36 NOT A MATCH

C. (38 + z + p)/2

38 + 5 + 3 =

46 NOT A MATCH

D. (38 + z - p)/2

38 + 5 - 3 =

40 MATCH

E. (48 + z + p)/2

48 + 5 + 3 =

56 NOT A MATCH

Answer