• Support PF! Buy your school textbooks, materials and every day products Here!

Same method not working in 2 age problems

  • Thread starter zak100
  • Start date
  • #1
zak100
Gold Member
402
9

Homework Statement



Q1. Lindsay is twice as old as she was 10 years ago. Kimberly is half as old as she will be in 10 years.

Find Lindsay’s age now?

Find Kimberly’s age now?

Q2.
In 8 years Tiffany will be 3 times as old as she is now. The number of years until Tiffany will be 6 times as old as she is now.

Homework Equations


Simple algebric equation of one variable

The Attempt at a Solution


Q1 Solution:
Let L = Lindsay’s age & K = Kimberly’s age

L=2(L-10)=>L=20

K=1/2(K+10)=>k=10

Q2 Solution:
T = 3(T+8)

But this is not correct. Some body guide me. The wordings of two questions are same but why same technique not working.


Zulfi.
 

Answers and Replies

  • #2
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,363
4,886
Q2 Solution:
T = 3(T+8)
How are you defining T here? Age now?
 
  • #3
33,075
4,776
Q2 Solution:
T = 3(T+8)

But this is not correct.
Because your equation is wrong.
Your equation says that Tiffany's age now is equal to 3 times her age in 8 years. That can't be true. People's ages normally get larger, not smaller.
 
  • #4
zak100
Gold Member
402
9
Hi,

I am able to find out the correct equation. The correct equation is:

T+8 = 3T

The complete question is:

In 8 years Tiffany will be 3 times as old as she is now. The number of years until Tiffany will be 6 times as old as she is now. Find out the number of years until Tiffany will be 6 times as old as she is now.


My solution is:

T+8 = 3T =>2T = 8 => T =4

6 times = 6 * 4= 24

Therefore number of years until Tiffany will be 6 times as old as she is now = 24-20 =20

Please tell me if its right or wrong.


Zulfi.
 
  • #5
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,363
4,886
Please tell me if its right or wrong.
It's right.
 
  • #6
33,075
4,776
Q2.
In 8 years Tiffany will be 3 times as old as she is now. The number of years until Tiffany will be 6 times as old as she is now.
My solution is:

T+8 = 3T =>2T = 8 => T =4
So, in the language of the problem, Tiffany's age right now is 4.
zak100 said:
6 times = 6 * 4= 24

Therefore number of years until Tiffany will be 6 times as old as she is now = 24-20 =20

Please tell me if its right or wrong.
There's no need to ask us to confirm whether your answer is correct or not. You should get in the habit of checking your answers. If you start out by defining your variables clearly, then it makes it easier to write correct equations as well as to check your solutions.

In this problem, Tiffany's age now is 4. How old will she be in 8 years? Will her age then be three times her age now? In 20 years how old will she be? Will her age by six times what it is now?
 

Related Threads for: Same method not working in 2 age problems

Replies
6
Views
16K
Replies
2
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
5
Views
882
  • Last Post
Replies
5
Views
437
  • Last Post
Replies
2
Views
9K
  • Last Post
Replies
9
Views
694
Replies
5
Views
2K
Top