Frank is 15 years younger then John. In 5 years John will be

Question

Frank is 15 years younger then John. In 5 years John will be twice as old as Frank. How old will Frank be in four years? 
 
A. 8 
B. 10 
C. 12 
D. 14 
E. 16

Bunuel · Answer

Frank is 15 years younger then John --> F+15=J;

In 5 years John will be twice as old as Frank (in 5 year John will be J+5 years old and Frank will be F+5 years old) --> J+5=2*(F+5) --> (F+15)+5=2*(F+5) --> F=10;

In 4 years Frank will be 10+4=14 years old.

Answer: D.

Hope it's clear.

Stoneface · Answer

This is where I made my mistake: J+5=2*(F+5). I was working J+5=2*F. Thanks!

liko21 · Answer

I like to work these kind of problems in columns

F | J
 ----------------------
Now  X-15  |  X

In 5 years X-15+5= X-10  |  X+5

twice as old means X+5=X-10=>X=25

But what we want is X-15+4 so 25-15+4=D

PS: The column is not clear enough in the post but I hope it is obvious

Salvetor · Answer

F = J-15
2(F+5) = J+5 >> 2F+10=J+5

So. F= 10

In four years,

F+4=14

JeffTargetTestPrep · Answer

We can create the equations:

F + 15 = J

and

J + 5 = 2(F + 5)

J + 5 = 2F + 10

J = 2F + 5

Substituting, we have:

F + 15 = 2F + 5

10 = F

So in 4 years Frank will be 14.

Answer: D

Abhishek009 · Answer

Capture.PNG j + 5 = 2(j - 10) j + 5 = 2j - 20 Or, j = 25 , So, Frank's age after 4 years will be j - 11 , ie 25 - 11 = 14 , Answer must be (D)

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