212°F
147°F
23.2 min
1) Initial temperature for t=0
T(0)=68+144e^(0)=68+144=212°F
2) After 15 min
T(15)=68+144e^(-0.04*15)=68+144e^(-0.6)=147°F
3) 125°F -> t=?
125=68+144e^(-0.04t)
144e^(-0.04t)=125-68=57
e^(-0.04t)=57/144=0.4 you can apply ln on both sides:
-0.04t=ln(0.4) solving you get t=23.3 min
Check the attached file for the answer.
All we have to do is multiply the numerator by the other numerator and the denominator by the other denominator.
11•2=22
98•99=9702
They are both even, so we can divide by two with both numbers.
11/4851
4851 can be divided by 11. So we can divide the top and bottom by 11.
1/441 is the product.
I used similarities in triangles
So it can be easier to solve your problem
