Need algebra help.?

Question

Bob's age is four times Michelle's age and Sara's age is half Bob's age. If their ages add up to 84, what is each persons age?

I'm trying to help my son with his homework and I haven't done this in a long time.

Answer 1

Honestly, this one is not really that hard, once you establish a system to get at the answer. We'll use the letters B, M, and S to stand for the ages of Bob, Michelle, and Sara. The statement of the problem tells us that:

B = 4 M
S = 1/2 B and therefore = 2 M
B + S + M = 84

So you have Michelle = M and
Bob = 4 M and
Sara = 1/2 B = 2 M
add them up and you have M + 4M + 2M = 7M = 84.
Divide 84 by 7 and you get M = 12.

Go back and substitute 12 for each M, and see what you get:

Michelle = M = 12
Bob = 4M = 48
Sara = 2M = 24
Total: 84

See, that wasn't so hard, was it?

Answer 2

You need to have a common variable to describe each person's age. In this case, everyone's age relates to Michelle's age, so you might call her age m.

Thus, Michelle's age = m

Since Bob is four times Michelle's age, his age = 4m.

Since Sara is half Bob's age, her age is 2m.

Now, all the ages are described in terms of a common variable. You also know that the sum of the ages is 84.

Thus you have:

m+4m+2m=84
7m=84
Dividing both sides of the equation by 7 gives you:
m=12

Thus, Michelle is 12 years old.

Since Bob is four times Michelle's age, his age is 48.

Since Sara is half Bob's age, her age is 24.

If you double check, you will see that the three ages add up to 84.

Good luck with the rest of your homework!

William
New York City

Answer 3

Okay, ready? Let Michelle be M. It says that Bob's age is four times Michelle's age. So Bob is 4M. It says that Sarah's age is half of Bob's age. If Bob is 4M, Sara is 2M. It says that their ages add up to 84. So M + 4M + 2M = 84.

7M = 84

Divide by 7 on both sides and you get ..

M= 12.

So Michelle is 12.

Bob is 4M, so Bob is 12 X 4, which is 48.

Sarah's age is 2M. So Sarah's age is 24.

Answer 4

Bob is 48, Michelle is 12, and Sara is 24.

Answer 5

Bob's age = 4M
Michelle's age = M
Sara's age = 0.5 (4M) = 2M
4M + M + 2M =84
7M = 84
M = 12
So Bob's age is 4M=48, Michelle's age is M=12, and Sara's age is 2M=24.

Write out each problem in words if that helps - good luck.

Answer 6

All you have to do is assign each person a variable, like the first letter of their name. Then go through the problem and make the two formulas (hint: "is" means = )

B=4M
S=1/2 B
B+M+S=84

Therefore, it's all substitution from there. Start with the first two equations (hint: B=4M ... so substitute 4M for B in the second formula.) But you should do the rest on your own. Good luck.

*Edit: Ok, everyone else gave you the answer anyways, but oh well. But word of advice, you'll never really learn it if you don't try to figure things out yourself.

Answer 7

do you know how 2 set up a guess and check table?
like this,

Michelle ][ Bob (m x 4) ][ Sara (b / 2) ][ total= 84 (m+b+s)

Answer 8

michelle's age is 12
bob's age is 48
sara age is 24

it all add up to 84

Answer 9

let: x= michaels age,
4x= bob's age
2x= sara's age....

x+4x+2x=84

7x= 84
x= 12..... therefor michael is 12, bobs age = 4x therefore, he is 48, saras age = 2x, therefor she is 24.

Answer 10

Bob = 4x
Michelle = x
Sara = (4x)/2 = 2x

4x+x+2x = 84
7x = 84
x = 12

Bob = 48
Michelle = 12
Sara = 24