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# Edexcel C3 Confusion watch

1. Question:

Parts a and b I am fine with. As for part c:

Working:

T=18 when t=70, T=12 when t=120

18-5=13=B*exp(-70*0.0124)
B=13*exp(0.868)=30.9 (3 s.f.)

Check with other values:
12-5=7
B=7*exp(1.488)=30.9 (3 s.f.)

Markscheme:

I may have the right final answer, but I can't see why you can't simply sub in values for T for corresponding t like I did above.
Then again, it did seem like three too easy marks.
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2. (Original post by Nuclear Ghost)
Question:

Parts a and b I am fine with. As for part c:

Working:

T=18 when t=70, T=12 when t=120

18-5=13=B*exp(-70*0.0124)
B=13*exp(0.868)=30.9 (3 s.f.)

Check with other values:
12-5=7
B=7*exp(1.488)=30.9 (3 s.f.)

Markscheme:

I may have the right final answer, but I can't see why you can't simply sub in values for T for corresponding t like I did above.
Then again, it did seem like three too easy marks.
it works both ways
ok even if not in the marking scheme
3. (Original post by TeeEm)
it works both ways
ok even if not in the marking scheme
Thank you.
4. (Original post by Nuclear Ghost)
Thank you.
no worries

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