Question 208974: When I am as old as my father is now, I will five times as old as my son is now. By then, my son will be eight years older than I am now. The sum of my father's age and my age is 100 years. How much older am I than my son?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! When I am as old as my father is now, I will five times as old as my son is now. By then, my son will be eight years older than I am now. The sum of my father's age and my age is 100 years. How much older am I than my son?
:
m = my age now
f = father's age now
s = son's age now
d = f - m; (me and dad's age difference)
:
"When I am as old as my father is now, I will five times as old as my son is now."
father now is 5 times son now
f = 5s
we can substitute 5s for f and we have difference of
d = 5s - m
:
"By then, my son will be eight years older than I am now."
(s + d) = m + 8
Substitute (5s-m) for d
s + (5s - m) = m + 8
6s - m - m = 8
6s - 2m = 8
:
"The sum of my father's age and my age is 100 years."
f + m = 100
Substitute 5s for f
5s + m = 100
Multiply this equation by 2 and add to eq: 6s - 2m = 8
10s + 2m = 200
6s - 2m = 8
----------------adding eliminates m, find s
16s = 208
s = 
s = 13 yrs is son's present age
then
5(13) = 65 yrs is father's present age
:
It's easy to find my age
65 + m = 100
m = 35 yrs is my age
;
;
Check solutions in the statement: (d = 65 - 35 = 30 yrs difference)
"By then, my son will be eight years older than I am now."
13 + 30 = 35 + 8
:
Dad: 65, me 35, son 13
|
|
|
