SOLUTION: "Grandpa how old are you?"Billy asked. His grndfather retorted,"why,the average age of you grandmother and me is seventy years,Billy." "But how old are you

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Question 2325: "Grandpa how old are you?"Billy asked. His grndfather retorted,"why,the average age of you grandmother and me is seventy years,Billy." "But how old are you_?" he asked again,seemiing impatient.
"Well,let me put it another way: I am twice as old as your grandmother was when I was her present age.Perhaps you can figure out both our ages by using some of that algebra you learned today." Scratching his head,Billy went to his room.
Answer by longjonsilver(2297) (Show Source):
You can put this solution on YOUR website!
define:
x = grandpa's age now
y = grandma's age now.
1.
--eqn1
2. when he was her age: he was y, she was y-(x-y) where (x-y) is the difference in their ages. Use numbers to check this..just make some up and look at how you would work it out with numbers.
x = 2(y-(x-y)) --eqn2. this is a tricky one to get.
Re-arranging gives...
x = 2(2y-x)
x = 4y - 2x
3x = 4y --eqn3
sub 1 into 3 for x, gives
3(140-y) = 4y
420-3y= 4y
7y=420
y=60
so x=80
check...grandma was 40 when he was her age now, 60. And Grandpa's current age of 80 is twice that..so correct.
jon.

SOLUTION: "Grandpa how old are you?"Billy asked. His grndfather retorted,"why,the average age of you grandmother and me is seventy years,Billy." "But how old are you_?" he asked again,seemii