+0  
 
0
298
1
avatar+103 

the brothers age is twice his sisters. in 6 years the brothers age will 5 times his sister age as she was 3 years ago. how old are they today?

math algebra
BlindxD  Aug 25, 2014

Best Answer 

 #1
avatar+3450 
+15

Let's have b = current brother's age and s = current sister's age.

The brothers age is twice his sisters age, so we have:

b = 2s

In 6 years, the brothers age will be 5 times his sisters age...as she was 3 years ago.

6 + b = 5(s-3)              ---Now just simplify a little bit

6 + b = 5s - 15

21 + b = 5s

 

So how we have two equations.

b = 2s 

and

21 + b = 5s

 

Let's solve this by elimiation. Multiply the first equation by a negative

b = 2s 

-b = -2s

21 + b = 5s          ---Second equation

21 = 3s

7 = s

 

The sisters age is 7. Let's put in this for s in the first equation and solve for b (which is the brothers age)

b = 2s 

b = 2(7)

b = 14

 

So the sister is 7 years old and the brother is 14 years old.

NinjaDevo  Aug 25, 2014
Sort: 

1+0 Answers

 #1
avatar+3450 
+15
Best Answer

Let's have b = current brother's age and s = current sister's age.

The brothers age is twice his sisters age, so we have:

b = 2s

In 6 years, the brothers age will be 5 times his sisters age...as she was 3 years ago.

6 + b = 5(s-3)              ---Now just simplify a little bit

6 + b = 5s - 15

21 + b = 5s

 

So how we have two equations.

b = 2s 

and

21 + b = 5s

 

Let's solve this by elimiation. Multiply the first equation by a negative

b = 2s 

-b = -2s

21 + b = 5s          ---Second equation

21 = 3s

7 = s

 

The sisters age is 7. Let's put in this for s in the first equation and solve for b (which is the brothers age)

b = 2s 

b = 2(7)

b = 14

 

So the sister is 7 years old and the brother is 14 years old.

NinjaDevo  Aug 25, 2014

10 Online Users

avatar
We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details