please help me with this problem, i'd like to know HOW to do this. please set this up for me!
Matthew is 3 times as old as Jenny. In 7 years, he will be twice as old as she will be the. How old is each now?
2007-12-03 16:14:09 · 10 answers · asked by tonetti@sbcglobal.net 2 in Science & Mathematics ➔ Mathematics
Let Jenny be x years old
Matthew = 3x
Matthew in 7 years = 3x + 7
Jenny in 7 years = x + 7
3x + 7 = 2(x + 7)
3x + 7 = 2x + 14
x = 7
Jenny is 7 years
Matthew is 21 years
2007-12-03 21:55:30 · answer #1 · answered by Como 7 · 1⤊ 0⤋
We'll use the variable "x" to represent Jenny, and "y" to represent Matthew.
Right now Matt is 3 times as old as Jenny, so...
y = 3x
In 7 years, he will be twice as old...
y + 7 = 2(x + 7)
...simplifies to...
y = 2x + 7
Now, set the equations for y equal to each other...
3x = 2x + 7
...solving you get...
x = 7
Plug that into one of the original equations...
y = 3x
y = 3(7)
y = 21
So right now Jenny is 7, and Matthew is 21
2007-12-03 16:20:56 · answer #2 · answered by ? 3 · 0⤊ 0⤋
Let x= Jenny's age
3x= matthews age
3x+7 Write a demostrative expression
=2(x+7) No turn it into an equation by adding 7 years
3x+7=2x+14 distributive property
x=7
Therefore Jenny is 7 and Matthew is 21.
2007-12-03 16:18:25 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Matthew is 3 times as old as Jenny:
say that mathiw's age now is x & Jenny's y, then:
x = 3y
In 7 years, he will be twice as old as she will be
{in 7 years mathiw will be (x+7) and Jenny will be (y+7)}
(x+7) = 2(y+7)
You have 2 equations and 2 variables. sole them:
x = 3y --> (1)
(x+7) = 2(y+7) --> (2)
substitute x with y in (2):
3y + 7 = 2y + 14
...
y = 7
and from (1)
x = 3*7
x = 21
there u go:
Matthew is 21 now and Jenny is 7 yo now
2007-12-03 16:23:25 · answer #4 · answered by riZi 3 · 0⤊ 0⤋
Let M be Matt's age
J be Jenny's age
Anywhere you see an "is" put an equal sign
M = 3*J Eqn (1)
in M+7 = 2*(J+7) Eqn (2)
Two equations, two variables - it can be solved.
Since you have M in terms of J from the first equation, substitute it into the second equation
3*J + 7 = 2*J + 14
J + 7 = 14
J = 7
Now substitute back into Eqn (1)
M = 3*(7)
M = 21
2007-12-03 16:19:39 · answer #5 · answered by mattmedfet 3 · 1⤊ 0⤋
Just in case you gotta work it out:
M=Matthew, J=Jenny =P
M= 3xJ
M+7=2(J+7)
M+7=25+14
M-2J=7
3J-27=7
So, Matthew is 21, and Jenny's 7. Get it?
2007-12-03 16:23:31 · answer #6 · answered by Sonia 2 · 0⤊ 0⤋
i did:
x=Jenny's age
3x(representing matt)
3x+7=2x
(3x=matt 3 times her age, 7=7years, 2x=means matt will be twice her age in 7 years)
if you solve you get x=-7 but obviously you cant be a negative age lol so, it means in she is 7 years old now and he is 21. in seven years she will be 14 and he will be 28.
hope this helps
2007-12-03 16:28:51 · answer #7 · answered by Teamx_xSwitzerland 3 · 0⤊ 0⤋
Mathew =x yrs
jenny=y yrs
x=3y 1st equation
x+7=2(y+7) 2nd equation
u hav 2 eqautions and 2 unknowns now solve!
now solving we get jenny is 7yr old & mathew is 21 yrs old!!!
2007-12-03 16:18:12 · answer #8 · answered by Tarun S 2 · 0⤊ 0⤋
7 and 21...took me a minute, sorry
2007-12-03 16:17:35 · answer #9 · answered by Anonymous · 0⤊ 1⤋
7+(3x)? im just taking a guess lol
2007-12-03 16:17:58 · answer #10 · answered by misticbaby21 4 · 0⤊ 1⤋