x Turn on thread page Beta
 You are Here: Home >< Maths

# Problem solving watch

1. A man runs to a telephone and back in 900 seconds. On the way to the telephone his speed is 5m/s and on his way back, his speed is 4m/s. find the distance to the telephone
2. Call the distance x.

Write an equation in x, then solve it to get the distance.
3. No idea but i would know if it was 200 times easier. Am i right or am I right
4. (Original post by Greatthinker)
No idea but i would know if it was 200 times easier. Am i right or am I right
I think you're trying to hint at the answer, which is not allowed, however your answer is wrong.
5. I've pm you instead morgan
6. Miatbailey did you get the question out in the end?
7. Don't mean to hijack the thread but since it's problem solving too

A cancer patient is injected with 250ml of a chemotherapy drug. Every 6hrs 32% of the drug passes out of her blood system. To compensate, a further 55ml dose is given every 6 hrs.

(1)find the recurrence relation for the amount of drugs in her blood stream.
(2) remaining drugs in her system after 24hrs.

I get trouble forming the recurrence relation.

Posted from TSR Mobile
8. (Original post by Arieisit)
Don't mean to hijack the thread but since it's problem solving too

A cancer patient is injected with 250ml of a chemotherapy drug. Every 6hrs 32% of the drug passes out of her blood system. To compensate, a further 55ml dose is given every 6 hrs.

(1)find the recurrence relation for the amount of drugs in her blood stream.
(2) remaining drugs in her system after 24hrs.

I get trouble forming the recurrence relation.

Posted from TSR Mobile
where f(x) is a function of x

Take each 6 hours as a step and think about how the volume of dosage changes each time.
9. (Original post by morgan8002)
where f(x) is a function of x

Take each 6 hours as a step and think about how the volume of dosage changes each time.
Yeah, I know what recurrence relations look like but I just get everything to add up when I try it so I know thats wrong so I'm asking for help.

10. (Original post by Arieisit)
Yeah, I know what recurrence relations look like but I just get everything to add up when I try it so I know thats wrong so I'm asking for help.

Yeah I didn't know where you got stuck.
The first part is that the drug passes out of her system. For this you need to multiply by something as 32% is lost each 6 hrs.

The second part is that you add 55 ml every 6 hours.

You can put these two effects into one relation.
11. (Original post by Arieisit)
Yeah, I know what recurrence relations look like but I just get everything to add up when I try it so I know thats wrong so I'm asking for help.

U0 = 250
U1 = 250*0.68 + 55

Etc
12. (Original post by TenOfThem)
...
TenOfThem I was trying to get them to work that out themselves.
13. (Original post by TenOfThem)
U0 = 250
U1 = 250*0.68 + 55

Etc
Why multiply by .68 and not .32?

Posted from TSR Mobile
14. (Original post by Arieisit)
Why multiply by .68 and not .32?

Posted from TSR Mobile
U1 is how much you have at that point

If you lose 32% how much do you have
15. (Original post by TenOfThem)
U1 is how much you have at that point

If you lose 32% how much do you have
Ok so I'm at

Posted from TSR Mobile
16. (Original post by Arieisit)
Ok so I'm at

Posted from TSR Mobile
The u3 is nonsense

U3 has 68% of the amount that was in at hour 6 plus 55
17. (Original post by Arieisit)
Ok so I'm at

Posted from TSR Mobile

and so on because the same relation occurs each time.
18. (Original post by morgan8002)

and so on because the same relation occurs each time.
Thank you for your help Morgan. I was actually helping a friend out but thanks for reminding me that I can be clueless to some A level questions even while at uni.

Posted from TSR Mobile
19. (Original post by Arieisit)
Thank you for your help Morgan. I was actually helping a friend out but thanks for reminding me that I can be clueless to some A level questions even while at uni.

Posted from TSR Mobile
I thought this was GCSE? Which module do people do this stuff in?
20. (Original post by morgan8002)
I thought this was GCSE? Which module do people do this stuff in?
GCSE? Nooo. What module? I'm not sure, at the moment.

Posted from TSR Mobile

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 15, 2015
Today on TSR

### Ask the House of Commons anything

The digital outreach team is online until 4pm!

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams