SOLUTION: Terri is two years older than Ginnie. Joan is twice Ginnie's age. How old is Ginnie if the sum of the squares of the three ages is 420?

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Question 410283: Terri is two years older than Ginnie. Joan is twice Ginnie's age. How old is Ginnie if the sum of the squares of the three ages is 420?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let t = Terri's age
Let g = Ginnie's age
Let j = Joan's age
given:
t+=+g+%2B+2
j+=+2g
t%5E2+%2B+g%5E2+%2B+j%5E2+=+420
--------------------
%28g+%2B+2%29%5E2+%2B+g%5E2+%2B+%282g%29%5E2+=+420
g%5E2+%2B+4g+%2B+4+%2B+g%5E2+%2B+4g%5E2+=+420
6g%5E2+%2B+4g+-+416+=+0
3g%5E2+%2B+2g+-+208+=+0
Use quadratic formula
g+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a+=+3
b+=+2
c+=+-208
g+=+%28-2+%2B-+sqrt%28+2%5E2-4%2A3%2A%28-208%29+%29%29%2F%282%2A3%29+
g+=+%28-2+%2B-+sqrt%28+4+%2B+2496+%29%29%2F+6+
g+=+%28-2+%2B+50%29%2F+6+
g+=+48%2F6
g+=+8
and
j+=+2g
j+=+16
and
t+=+g+%2B+2
t+=+10
Ginnie is 8 yrs old
check answer:
t%5E2+%2B+g%5E2+%2B+j%5E2+=+420
10%5E2+%2B+8%5E2+%2B+16%5E2+=+420
100+%2B+64+%2B+256+=+420
420+=+420
OK