Mary's and Bob's ages combined are twice Jane's age. Mary is 8 years older than Bob. Jane's age plus Bob's age is 20 years. How old are they?
2006-10-24 02:42:38 · 6 answers · asked by Sasha 2 in Science & Mathematics ➔ Mathematics
mary = 16
bob = 8
jane = 12
full solution:
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mary + bob = 2(jane)
mary = bob + 8
jane + bob = 20
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bob = mary - 8
bob = 20 - jane
20 - jane = mary - 8
mary = 28 - jane
jane = 28 - mary
mary + bob = 2(28-mary)
mary + bob = 56 - 2(mary)
3(mary) + bob = 56
3(mary) + mary - 8 = 56
4(mary) = 64
mary = 16
bob = mary - 8
bob = 8
16 + 8 = 2(jane)
jane = 24/2
jane = 12
2006-10-24 02:56:44 · answer #1 · answered by Ricky the Kid 4 · 1⤊ 0⤋
Mary = 16, Bob = 8, Jane = 12
2006-10-24 02:50:56 · answer #2 · answered by jem 1 · 0⤊ 0⤋
Bob is 8, Mary is 16 and Jane is 12
2006-10-24 02:46:42 · answer #3 · answered by Shannon L - Gavin's Mommy 6 · 0⤊ 0⤋
need two variables
X and Y
Bob = X
Mary = X + 8
Jane = Y
we know mary and bob's combine is twice the age of jane
therefore
X + X + 8 = 2Y
solve for y
2X + 8 = 2Y
X + 8 = Y hold this
now we know jane's age plus bob's age is
x + x + 4 = 20
solve for x:
2x + 4 = 20
2x = 16
x = 8 now plug this back in
bob = 8
mary = 8 +8 = 16
jane = y = 4 + 8 = 12
let's check
Mary and bob ages combine are twice jane's age
8 + 16 = 2(12)
24 = 24 OK
Mary is 8 year's older than bob
bob = 8
Mary = 8+8=16 OK
Jane's age plus bob's age is 20:
12 + 8 = 20 OK
we passed!
2006-10-24 03:00:28 · answer #4 · answered by Arkane Steelblade 4 · 0⤊ 0⤋
Marry = M
Bob =B
Jane = J
M+B= 2J
J+B=20 or B= (20-J)
B+8+B=2J or 2B +8 =2J or 2(20-J) + 8 =2J or
40-2J+8=2J or 48=4J or J=12
Wen J=12 then B=8 and M=16
2006-10-24 02:59:46 · answer #5 · answered by MY Regards to All 4 · 0⤊ 0⤋
marys 16
bob 8
jane 12
2006-10-24 02:47:57 · answer #6 · answered by jorge 1 · 0⤊ 0⤋