SOLUTION: Robert is thinking that his father is 7 years older than twice his age, his grandfather is 4 years less than twice his father’s age. If Robert’s grandfather is 70 years old, ho

Question 1164747: Robert is thinking that his father is 7 years older than twice his age, his grandfather is 4 years less than twice his father’s age. If Robert’s grandfather is 70 years old, how old is Robert ?
Found 4 solutions by Alan3354, ankor@dixie-net.com, greenestamps, MathTherapy:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
Robert is thinking that his father is 7 years older than twice his age, his grandfather is 4 years less than twice his father’s age. If Robert’s grandfather is 70 years old, how old is Robert ?
-----------------
R = Robert's age
F = 2R + 7
G = 2F - 4 = 70
-----
Solve for F, then solve for R
Answer by ankor@dixie-net.com(22740)   (Show Source): You can put this solution on YOUR website!
Robert is thinking that his father is 7 years older than twice his age,
f = 2r + 7
his grandfather is 4 years less than twice his father’s age.
g = 2f - 4
If Robert’s grandfather is 70 years old,
g = 70
:
Replace g with 70 in the 2nd equation
2f - 4 = 70
2f = 70 + 4
2f = 74
f = 74/2
f = 37
:
how old is Robert ?
in the first equation, replace f with 37
2r + 7 = 37
2r = 37 - 7
2r = 30
r = 30/2
r = 15 yrs is Robert's age
:
:

Answer by greenestamps(13203)   (Show Source): You can put this solution on YOUR website!

x = Robert's age
y = his father's age
70 = his grandfather's age

(1) His grandfather's age, 70, is 4 less than twice his father's age:

Solve to find his father's age, y.

(2) Robert's father is 7 years older than twice his age.

Substitute the value of y found in step (1) and solve to find Robert's age.

Answer by MathTherapy(10555)   (Show Source): You can put this solution on YOUR website!

Robert is thinking that his father is 7 years older than twice his age, his grandfather is 4 years less than twice his father’s age. If Robert’s grandfather is 70 years old, how old is Robert?

Let Richard's age be R
Then his father's is: 2R + 7, and his grandfather's is: 2(2R + 7) - 4
We then get: 2(2R + 7) - 4 = 70
4R + 14 - 4 = 70
4R = 60
Richard or
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