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    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
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    Call the distance x.

    Write an equation in x, then solve it to get the distance.
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    No idea but i would know if it was 200 times easier. Am i right or am I right
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    (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.
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    I've pm you instead morgan
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    Miatbailey did you get the question out in the end?
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    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.

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    (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
    x_{n+1} = f(x_{n}) 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.
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    (Original post by morgan8002)
    x_{n+1} = f(x_{n}) 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.

    I had some thing like U_6 = U_1 - 73
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    (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.

    I had some thing like U_6 = U_1 - 73
    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.
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    (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.

    I had some thing like U_6 = U_1 - 73
    U0 = 250
    U1 = 250*0.68 + 55

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

    Etc
    Why multiply by .68 and not .32?

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    (Original post by Arieisit)
    Why multiply by .68 and not .32?

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    U1 is how much you have at that point

    If you lose 32% how much do you have
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    (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

    U_1 = 250



U_2 = 250 \times 0.68 + 55



U_3 = 250 \times 0.36 + 55



U_n = 250( ? ) + 55



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    (Original post by Arieisit)
    Ok so I'm at

    U_1 = 250



U_2 = 250 \times 0.68 + 55



U_3 = 250 \times 0.36 + 55



U_n = 250( ? ) + 55



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    The u3 is nonsense

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

    U_1 = 250



U_2 = 250 \times 0.68 + 55



U_3 = 250 \times 0.36 + 55



U_n = 250( ? ) + 55



    Posted from TSR Mobile
    

U_1 = 250

U_2 = (0.68)U_1 + 55

U_3 = (0.68)U_2 + 55
    and so on because the same relation occurs each time.
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    (Original post by morgan8002)
    

U_1 = 250

U_2 = (0.68)U_1 + 55

U_3 = (0.68)U_2 + 55
    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.

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    (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.

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    I thought this was GCSE? Which module do people do this stuff in?
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    (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
 
 
 
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