MaTh PrObLeMs?

Question

Please give me the step-by-step to how u did this problem..





She gave us like 20 of these kind pf problems!! Arrgg so could you just tell me each step how you got this answer. Thank you so much.. i will give you best answer points for your help too =)



Six years agoBob was four times as old as Perry. In nine years he will be 3/2 as old. Find the ages of Bob and Perry today.

Answer 1

You asked for step by step...you got it!

Step One:

Define variables. In other words, let's make the problem a little shorter.

"Six years ago, Bob was four times..." blah blah.

So, let's have Bob's age be "x"

While we're at it, let's make Perry's age be "y".

Step two:

Turn the variables into an equation, based on what was given.

Six years ago, Bob was.... That means that Bob's age (x), six years ago...let's subtract six.

x - 6

Was or is means " = "

x - 6 =

He was four times as old as perry.

So, if Perry is "y" we need four times that to be the same, and it was six years ago, so y-6

x -6 = 4(y-6)

Now, on to the second equation.

"In nine years, he will be 3/2 as old."

Once again, Bob's age is x, so in 9 years he'll be x+9. In the same way, he'll only be 3/2 as old as Perry or 3/2y

So we have: x + 9 = 3/2(y+9)

Now we have two equations:

x -6 = 4(y-6)

and

x + 9 = 3/2(y+9)

Let's expand these to:

x - 6 = 4y-24

x = 4y -18

and

x + 9 = 3/2 y + 27/2

x = 3/2 y + 9/2

Step 3: Eliminate one of the variables.

We normally do this by multiplying by something to make a variable opposite and the same, so when you get to the next step, you can get rid of one of the variables. Notice in this problem we have two "x's". If we multiply one of the equations by "-1" the x will be come -x. When we add x and -x it will cancel out.

What if it was 2x and 4x? We'd multiply the equation where the 2x was by -2 and then it would become -4x and be able to cancel out? Get it?

Okay...let's multiply that second equation by -1.

x = 3/2 y + 9/2 becomes

-x = -3/2y -9/2

and we still have

x = 4y -18

Step 4: Add the equations.

Let's add them like any other addition problem.

x = 4y -18
-x = -3/2y -9/2


- x + x will cancel out

4y - 3/2 y = 5/2 y

-18 - 9/2 = 45/2

So we have:

0 = 5/2 y -45/2

45/2 = 5/2 y

Multiply by 2

45 = 5y

y = 9 so Perry is 9 years old.


Plug it back in to find Bob's age.

x = 4y -18
x = 4(9) - 18

So, Bob is 18.

Hope you can follow similar steps for all your problems.

Regards,

Mysstere

Answer 2

ok, take it easy, do not make yourself confused, alright?
you got the info. of Bob and Perry differences
let Bob's age is x
Perry's age is y
and 6 years ago, Bob's age= 4* Perry's age
x - 6 = 4(y - 6)

in 9 years, Bob's age = 3/2 Perrry's age
x + 9= 3/2(y + 9)

now, you get 2 equations, and solve for x and y, you would get the answers you want:
x - 6 = 4(y - 6)
x = 4y - 24 + 6 = 4y - 18

x + 9= 3/2(y + 9)
x = 3/2 y + 27/2 - 9 = 3/2 y + 9/2

4y - 18 = 3/2 y + 9/2
4y - 3/2 y = 18 + 9/2
5/2 y = 45/2
y = 9

x = 4y - 18 = 4(9) - 18 = 36-18 = 18

so Bob's age is 18 and Perry's age is 9 now :)

Answer 3

Please check your equation. I wrote a big answer for you and something seems wrong. Are you sure it is 3/2 as old and not 2/3 as old?

Answer 4

please give me your tm cel number and i will help you. we will have a free tutorial in math. janus