Correct Method for Solving these questions

Thread Starter

zulfi100

Joined Jun 7, 2012
656
Hi,
I solved a question:

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

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

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


Now consider another question:

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.

I am using the same method, generating the equation:

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.
 

dl324

Joined Mar 30, 2015
12,442
Reread the description for Kimberly and compare the equation for her to the one you wrote for Tiffany.
 

WBahn

Joined Mar 31, 2012
26,398
Hi,
I solved a question:

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

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

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


Now consider another question:

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.

I am using the same method, generating the equation:

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.
You seem to have a couple of problems. First, you aren't solving for Tiffany's current age correct.

Hint: Assuming that T is Tiffany's current age, your equation says that she is currently 3 times as old as she will be 8 years from now.

Beyond that, Q2 isn't asking for how old Tiffany is now. It seems to be asking for how long it will be until she is 6 times as old as she is now.
 

Thread Starter

zulfi100

Joined Jun 7, 2012
656
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.
 

WBahn

Joined Mar 31, 2012
26,398
You shouldn't need to ask others if your answer is correct or not. You should be able to determine, from the proposed answer, whether it is right or wrong. That's one of the great beauties of science and engineering in most cases.

You are saying that Tiffany is currently 4 years old. In eight years she will be 12 years old. Is that three times as old as she is now? You are saying that the answer to the question is 20 years because in 20 years she will be 6 times as old as she is now. Let's see. In 20 years she will be 24 years old. Is that six times as old as she is now? If so, then it would seem that the answer is correct.
 

dl324

Joined Mar 30, 2015
12,442
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.
How did you derive the last equation?

You arrived at the correct answer, but I wouldn't have used your method.
 

MrAl

Joined Jun 17, 2014
7,959
Hi,

With the recent announcement that obesity in the US had increased by 10 times in children over the past 40 years, a related question might be:
Sally weighs 10 times more than she did 2 years ago and 1/10 as much as she will in 2 more years. How much will Sally weigh in 10 years? For extra credit, how many planets will get caught in her gravitational field by the time she is 30 years old? :)
 

joeyd999

Joined Jun 6, 2011
4,477
Hi,

With the recent announcement that obesity in the US had increased by 10 times in children over the past 40 years, a related question might be:
Sally weighs 10 times more than she did 2 years ago and 1/10 as much as she will in 2 more years. How much will Sally weigh in 10 years? For extra credit, how many planets will get caught in her gravitational field by the time she is 30 years old? :)
Why are you hatin' on Sally? Are you cacomorphobic?

Check your skinny privilege. Until you've walked a mile in her exceptionally large shoes, you've got no right to criticize.
 
Last edited:

MrAl

Joined Jun 17, 2014
7,959
Why are you hatin' on Sally? Are you cacomorphobic?

Check your skinny privilege. Until you've walked a mile in her exceptionally large shoes, you've got no right to criticize.
Hello,

No hate from here, perhaps some coming from your end? The problem is not mine either but if something is not done about it more and more people will die from this problem.

I'll check whatever i want to check, when i want to check it, and wont check anything i dont want to check whenever i dont want to check it, but thanks for the offer Mr PC. For example, i have to watch my weight too.
 
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